- Rheumatoid Arthritis
- Allergy and Immunology
Chief, Division of Immunology and Rheumatology, Stanford University School of Medicine (2013 - Present)
Professional Education:University of Heidelberg (1988) Germany
Fellowship:Stanford University - Immunology/Rheumatology (1986) CA
Residency:Hannover Medical School (1984)
Fellowship:Heidelberg University German Cancer Research Center (1981)
Professional Education:University of Bonn (1980)
Medical Education:University of Aachen (1979)
Current Research and Scholarly Interests
Telomere biology and genomic stress in autoimmunity and inflammation
Independent Studies (10)
- Directed Reading in Immunology
IMMUNOL 299 (Aut, Win, Spr, Sum)
- Directed Reading in Medicine
MED 299 (Aut)
- Early Clinical Experience in Immunology
IMMUNOL 280 (Aut, Win, Spr, Sum)
- Early Clinical Experience in Medicine
MED 280 (Win)
- Graduate Research
IMMUNOL 399 (Aut, Win, Spr, Sum)
- Graduate Research
MED 399 (Aut)
- Medical Scholars Research
MED 370 (Aut)
- Teaching in Immunology
IMMUNOL 290 (Aut, Win, Spr, Sum)
- Undergraduate Research
IMMUNOL 199 (Aut, Win, Spr, Sum)
- Undergraduate Research
MED 199 (Aut)
- Directed Reading in Immunology
Cardiorheumatology: cardiac involvement in systemic rheumatic disease
NATURE REVIEWS CARDIOLOGY
2015; 12 (3): 168-176
Autoimmune rheumatic diseases can affect the cardiac vasculature, valves, myocardium, pericardium, and conduction system, leading to a plethora of cardiovascular manifestations that can remain clinically silent or lead to substantial cardiovascular morbidity and mortality. Although the high risk of cardiovascular pathology in patients with autoimmune inflammatory rheumatological diseases is not owing to atherosclerosis alone, this particular condition contributes substantially to cardiovascular morbidity and mortality-the degree of coronary atherosclerosis observed in patients with rheumatic diseases can be as accelerated, diffuse, and extensive as in patients with diabetes mellitus. The high risk of atherosclerosis is not solely attributable to traditional cardiovascular risk factors: dysfunctional immune responses, a hallmark of patients with rheumatic disorders, are thought to cause chronic tissue-destructive inflammation. Prompt recognition of cardiovascular abnormalities is needed for timely and appropriate management, and aggressive control of traditional risk factors remains imperative in patients with rheumatic diseases. Moreover, therapies directed towards inflammatory process are crucial to reduce cardiovascular disease morbidity and mortality. In this Review, we examine the multiple cardiovascular manifestations in patients with rheumatological disorders, their underlying pathophysiology, and available management strategies, with particular emphasis on the vascular aspects of the emerging field of 'cardiorheumatology'.
View details for Web of Science ID 000350107600006
View details for PubMedID 25533796
- T-cell metabolism in autoimmune disease ARTHRITIS RESEARCH & THERAPY 2015; 17
Visual Manifestations in Giant Cell Arteritis: Trend over 5 Decades in a Population-based Cohort.
journal of rheumatology
2015; 42 (2): 309-315
To evaluate clinical characteristics, treatment, and outcomes of patients with visual changes from giant cell arteritis (GCA) and to examine trends over the last 5 decades.We reviewed the medical records of a population-based cohort of patients with GCA diagnosed between 1950 and 2004. The clinical, ophthalmological, and laboratory features of patients with visual manifestations attributable to GCA were compared to patients without visual complications. Trends over time were examined using logistic regression modeling adjusted for age and sex.In a cohort of 204 cases of GCA (mean age 76.0 ± 8.2 yrs, 80% female), visual changes from GCA were observed in 47 patients (23%), and 4.4% suffered complete vision loss. A higher proportion of patients with visual manifestations reported jaw claudication than did patients without visual changes (55% vs 38%, p = 0.04). Over a period of 55 years, we observed a significant decline in the incidence of visual symptoms due to GCA. There was a lower incidence of ischemic optic neuropathy in the 1980-2004 cohort vs 1950-1979 (6% vs 15%, p = 0.03). Patients diagnosed in later decades were more likely to recover from visual symptoms (HR 1.34, 95% CI 1.06-1.71). Chances of recovery were poor in patients with anterior ischemic optic neuropathy or complete vision loss.Incidence of visual symptoms has declined over the past 5 decades, and chances of recovery from visual symptoms have improved. However, complete loss of vision is essentially irreversible. Jaw claudication is associated with higher likelihood of development of visual symptoms.
View details for DOI 10.3899/jrheum.140188
View details for PubMedID 25512481
- Diversity and clonal selection in the human T-cell repertoire PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2014; 111 (36): 13139-13144
- Clinical practice. Giant-cell arteritis and polymyalgia rheumatica. New England journal of medicine 2014; 371 (1): 50-57
- Giant-Cell Arteritis and Polymyalgia Rheumatica NEW ENGLAND JOURNAL OF MEDICINE 2014; 371 (1): 50-57
Mechanisms shaping the naive T cell repertoire in the elderly - Thymic involution or peripheral homeostatic proliferation?
2014; 54: 71-74
The ability of the human immune system to repel infections is drastically diminished with age. Elderly individuals are more susceptible to new threats and are less able to control endogenous infections. The thymus, which is the sole source of new T cells, has been proposed as a target for regenerative efforts to improve immune competence, as thymic activity is dramatically reduced after puberty. In this review, we review the role of the thymus in the maintenance of T cell homeostasis throughout life and contrast the differences in mice and humans. We propose that in humans, lack of thymic T cell generation does not explain a decline in T cell receptor diversity nor would thymic rejuvenation restore diversity. Initial studies using next generation sequencing are beginning to establish lower boundaries of T cell receptor diversity. With increasing sequencing depth and the development of new statistical models, we are now in the position to test this model and to assess the impact of age on T cell diversity and clonality.
View details for DOI 10.1016/j.exger.2014.01.005
View details for Web of Science ID 000334526500012
Targets of Immune Regeneration in Rheumatoid Arthritis
MAYO CLINIC PROCEEDINGS
2014; 89 (4): 563-575
Many of the aging-related morbidities, including cancer, cardiovascular disease, neurodegenerative disease, and infectious susceptibility, are linked to a decline in immune competence with a concomitant rise in proinflammatory immunity, placing the process of immune aging at the center of aging biology. Immune aging affects individuals older than 50 years and is accelerated in patients with the autoimmune disease rheumatoid arthritis. Immune aging results in a marked decline in protective immune responses and a parallel increase in tissue inflammatory responses. By studying immune cells in patients with rheumatoid arthritis, several of the molecular underpinnings of the immune aging process have been delineated, such as the loss of telomeres and inefficiencies in the repair of damaged DNA. Aging T cells display a series of abnormalities, including the unopposed up-regulation of cytoplasmic phosphatases and the loss of glycolytic competence, that alter their response to stimulating signals and undermine their longevity. Understanding the connection between accelerated immune aging and autoimmunity remains an area of active research. With increasing knowledge of the molecular pathways that cause immunosenescence, therapeutic interventions can be designed to slow or halt the seemingly inevitable deterioration of protective immunity with aging.
View details for DOI 10.1016/j.mayocp.2014.01.020
View details for Web of Science ID 000333528700021
View details for PubMedID 24684878
Regulatory T Cells and the Immune Aging Process: A Mini-Review
2014; 60 (2): 130-137
Constant exposure to new and persisting antigens and the need to replace cellular attrition with newly built cells lead to profound remodeling of the immune system after the age of 50 years. The impact of the immunosenescence process varies amongst the different cellular subsets represented within the immune system. Emerging data suggest that progressive aging significantly affects frequencies, subset distribution and functional competence of regulatory T cells (Tregs). Given the central role of Tregs in immune homeostasis, age-related loss of Treg function would be predicted to cause excessive immunity, encountered in elderly humans as a syndrome of chronic, smoldering inflammation as well as the age-related increase in the risk for autoimmunity. Conversely, age-dependent gain of Treg activity would result in failing immunity, such as the rising risk of malignancies and infections amongst the elderly. Emerging data suggest that some Treg populations, specifically naturally occurring Tregs, seem to accumulate with advancing age, whereas inducible Tregs appear to be less available in the older host. More studies are necessary to elucidate functional competence of old Tregs, with an emphasis on comparing the efficacy of young and old Tregs for defined functional domains. Mechanisms of declining Treg inducibility are not understood, but may provide an opportunity for targeted immunomodulation in the elderly. On the horizon is the potential to develop novel therapeutic interventions that target Tregs to make the elderly more efficient in fighting cancers and infections and dampen the risk for senescence-associated inflammation.
View details for DOI 10.1159/000355303
View details for Web of Science ID 000331773700006
View details for PubMedID 24296590
T cell-macrophage interactions and granuloma formation in vasculitis.
Frontiers in immunology
2014; 5: 432-?
Granuloma formation, bringing into close proximity highly activated macrophages and T cells, is a typical event in inflammatory blood vessel diseases, and is noted in the name of several of the vasculitides. It is not known whether specific properties of the microenvironment in the blood vessel wall or the immediate surroundings of blood vessels contribute to granuloma formation and, in some cases, generation of multinucleated giant cells. Granulomas provide a specialized niche to optimize macrophage-T cell interactions, strongly activating both cell types. This is mirrored by the intensity of the systemic inflammation encountered in patients with vasculitis, often presenting with malaise, weight loss, fever, and strongly upregulated acute phase responses. As a sophisticated and highly organized structure, granulomas can serve as an ideal site to induce differentiation and maturation of T cells. The granulomas possibly seed aberrant Th1 and Th17 cells into the circulation, which are known to be the main pathogenic cells in vasculitis. Through the induction of memory T cells, aberrant innate immune responses can imprint the host immune system for decades to come and promote chronicity of the disease process. Improved understanding of T cell-macrophage interactions will redefine pathogenic models in the vasculitides and provide new avenues for immunomodulatory therapy.
View details for DOI 10.3389/fimmu.2014.00432
View details for PubMedID 25309534
T-cell aging in rheumatoid arthritis
CURRENT OPINION IN RHEUMATOLOGY
2014; 26 (1): 93-100
With progressive age, the immune system and the propensity for abnormal immunity change fundamentally. Individuals greater than 50 years of age are not only more susceptible to infection and cancer, but also at higher risk for chronic inflammation and immune-mediated tissue damage. The process of immunosenescence is accelerated in rheumatoid arthritis (RA).Premature T-cell senescence occurs not only in RA, but also has been involved in morbidity and mortality of chronic HIV infection. Senescent cells acquire the 'senescence-associated secretory phenotype', which promotes and sustains tissue inflammation. Molecular mechanisms underlying T-cell aging are beginning to be understood. In addition to the contraction of T-cell diversity because of uneven clonal expansion, senescent T cells have defects in balancing cytoplasmic kinase and phosphatase activities, changing their activation thresholds. Also, leakiness in repairing DNA lesions and uncapped telomeres imposes genomic stress. Age-induced changes in the tissue microenvironment may alter the T-cell responses.Gain-of-function and loss-of-function in senescent T cells undermine protective immunity and create the conditions for chronic tissue inflammation, a combination typically encountered in RA. Genetic programs involved in T-cell signaling and DNA repair are of high interest in the search for underlying molecular defects.
View details for DOI 10.1097/BOR.0000000000000011
View details for Web of Science ID 000328818500014
View details for PubMedID 24296720
Immune mechanisms in medium and large-vessel vasculitis
NATURE REVIEWS RHEUMATOLOGY
2013; 9 (12): 731-740
Vasculitis of the medium and large arteries, most often presenting as giant cell arteritis (GCA), is an infrequent, but potentially fatal, type of immune-mediated vascular disease. The site of the aberrant immune reaction, the mural layers of the artery, is strictly defined by vascular dendritic cells, endothelial cells, vascular smooth muscle cells and fibroblasts, which engage in an interaction with T cells and macrophages to, ultimately, cause luminal stenosis or aneurysmal wall damage of the vessel. A multitude of effector cytokines, all known as critical mediators in host-protective immunity, have been identified in vasculitic lesions. Two dominant cytokine clusters--the IL-6-IL-17 axis and the IL-12-IFN-γ axis--have been linked to disease activity. These two clusters seem to serve different roles in the vasculitic process. The IL-6-IL-17 cluster is highly responsive to standard corticosteroid therapy, whereas the IL-12-IFN-γ cluster is resistant to steroid-mediated immunosuppression. The information exchange between vascular and immune cells and stabilization of the vasculitic process involves members of the Notch receptor and ligand family. Focusing on elements in the tissue context of GCA, instead of broadly suppressing host immunity, might enable a more tailored therapeutic approach that avoids unwanted adverse effects of aggressive immunosuppression.
View details for DOI 10.1038/nrrheum.2013.161
View details for Web of Science ID 000328126000006
View details for PubMedID 24189842
Phosphofructokinase deficiency impairs ATP generation, autophagy, and redox balance in rheumatoid arthritis T cells
JOURNAL OF EXPERIMENTAL MEDICINE
2013; 210 (10): 2119-2134
In the HLA class II-associated autoimmune syndrome rheumatoid arthritis (RA), CD4 T cells are critical drivers of pathogenic immunity. We have explored the metabolic activity of RA T cells and its impact on cellular function and fate. Naive CD4 T cells from RA patients failed to metabolize equal amounts of glucose as age-matched control cells, generated less intracellular ATP, and were apoptosis-susceptible. The defect was attributed to insufficient induction of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3), a regulatory and rate-limiting glycolytic enzyme known to cause the Warburg effect. Forced overexpression of PFKFB3 in RA T cells restored glycolytic flux and protected cells from excessive apoptosis. Hypoglycolytic RA T cells diverted glucose toward the pentose phosphate pathway, generated more NADPH, and consumed intracellular reactive oxygen species (ROS). PFKFB3 deficiency also constrained the ability of RA T cells to resort to autophagy as an alternative means to provide energy and biosynthetic precursor molecules. PFKFB3 silencing and overexpression identified a novel extraglycolytic role of the enzyme in autophagy regulation. In essence, T cells in RA patients, even those in a naive state, are metabolically reprogrammed with insufficient up-regulation of the glycolytic activator PFKFB3, rendering them energy-deprived, ROS- and autophagy-deficient, apoptosis-sensitive, and prone to undergo senescence.
View details for DOI 10.1084/jem.20130252
View details for Web of Science ID 000324813000018
View details for PubMedID 24043759
Understanding immunosenescence to improve responses to vaccines
2013; 14 (5): 428-436
In the older adult, the benefits of vaccination to prevent infectious disease are limited, mainly because of the adaptive immune system's inability to generate protective immunity. The age-dependent decrease in immunological competence, often referred to as 'immunosenescence', results from the progressive deterioration of innate and adaptive immune responses. Most insights into mechanisms of immunological aging have been derived from studies of mouse models. In this Review, we explore how well such models are applicable to understanding the aging process throughout the 80-100 years of human life and discuss recent advances in identifying and characterizing the mechanisms that underlie age-associated defective adaptive immunity in humans.
View details for DOI 10.1038/ni.2588
View details for Web of Science ID 000317732100007
View details for PubMedID 23598398
IL-7-and IL-15-Mediated TCR Sensitization Enables T Cell Responses to Self-Antigens
JOURNAL OF IMMUNOLOGY
2013; 190 (4): 1416-1423
Regulation of the ERK pathway is intimately involved in determining whether TCR stimulation is productive or induces anergy. T cells from patients with rheumatoid arthritis (RA) have increased ERK responsiveness, which may be relevant for disease pathogenesis. Inflammatory cytokines such as TNF-α did not reproduce the TCR hypersensitivity typical for RA in T cells from healthy individuals. In contrast, priming with the homeostatic cytokines (HCs) IL-7 and IL-15 amplified ERK phosphorylation to TCR stimulation 2- to 3-fold. The underlying mechanism involved a priming of the SOS-dependent amplification loop of RAS activation. The sensitization of the TCR signaling pathway has downstream consequences, such as increased proliferation and preferential Th1 differentiation. Importantly, priming with IL-7 or IL-15 enabled T cell responses to autoantigens associated with RA. Production of HCs is induced in lymphopenic conditions, which have been shown to predispose for autoimmunity and which appear to be present in the preclinical stages of RA. We propose that HCs, possibly induced by lymphopenia, decrease the signaling threshold for TCR activation and are thereby partly responsible for autoimmunity in RA.
View details for DOI 10.4049/jimmunol.1201620
View details for Web of Science ID 000314825400005
View details for PubMedID 23325887
The janus head of T cell aging - autoimmunity and immunodeficiency.
Frontiers in immunology
2013; 4: 131-?
Immune aging is best known for its immune defects that increase susceptibility to infections and reduce adaptive immune responses to vaccination. In parallel, the aged immune system is prone to autoimmune responses and many autoimmune diseases increase in incidence with age or are even preferentially encountered in the elderly. Why an immune system that suboptimally responds to exogenous antigen fails to maintain tolerance to self-antigens appears to be perplexing. In this review, we will discuss age-associated deviations in the immune repertoire and the regulation of signaling pathways that may shed light on this conundrum.
View details for DOI 10.3389/fimmu.2013.00131
View details for PubMedID 23761790
Decline in miR-181a expression with age impairs T cell receptor sensitivity by increasing DUSP6 activity
2012; 18 (10): 1518-U113
The ability of the human immune system to respond to vaccination declines with age. We identified an age-associated defect in T cell receptor (TCR)-induced extracellular signal-regulated kinase (ERK) phosphorylation in naive CD4(+) T cells, whereas other signals, such as ? chain-associated protein kinase 70 (ZAP70) and phospholipase C-?1 phosphorylation, were not impaired. The defective ERK signaling was caused by the dual specific phosphatase 6 (DUSP6), whose protein expression increased with age due to a decline in repression by miR-181a. Reconstitution of miR-181a lowered DUSP6 expression in naive CD4(+) T cells in elderly individuals. DUSP6 repression using miR-181a or specific siRNA and DUSP6 inhibition by the allosteric inhibitor (E)-2-benzylidene-3-(cyclohexylamino)-2,3-dihydro-1H-inden-1-one improved CD4(+) T cell responses, as seen by increased expression of activation markers, improved proliferation and supported preferential T helper type 1 cell differentiation. DUSP6 is a potential intervention target for restoring T cell responses in the elderly, which may augment the effectiveness of vaccination.
View details for DOI 10.1038/nm.2963
View details for Web of Science ID 000309587500030
View details for PubMedID 23023500
Metabolic Reprogramming of Autoimmune T Cells in Rheumatoid Arthritis
WILEY-BLACKWELL. 2012: S1130-S1131
View details for Web of Science ID 000309748306175
Signaling pathways in aged T cells - A reflection of T cell differentiation, cell senescence and host environment
SEMINARS IN IMMUNOLOGY
2012; 24 (5): 365-372
With increasing age, the ability of the immune system to protect against new antigenic challenges or to control chronic infections erodes. Decline in thymic function and cumulating antigenic experiences of acute and chronic infections threaten T cell homeostasis, but insufficiently explain the failing immune competence and the increased susceptibility for autoimmunity. Alterations in signaling pathways in the aging T cells account for many of the age-related defects. Signaling threshold calibrations seen with aging frequently built on mechanisms that are operational in T cell development and T cell differentiation or are adaptations to the changing environment in the aging host. Age-related changes in transcription of receptors and signaling molecules shift the balance towards inhibitory pathways, most dominantly seen in CD8 T cells and to a lesser degree in CD4 T cells. Prominent examples are the expression of negative regulatory receptors of the CD28 and the TNF receptor superfamilies as well the expression of various cytoplasmic and nuclear dual-specific phosphatases.
View details for DOI 10.1016/j.smim.2012.04.003
View details for Web of Science ID 000311017700009
View details for PubMedID 22560928
The Immunopathology of Giant Cell Arteritis: Diagnostic and Therapeutic Implications
JOURNAL OF NEURO-OPHTHALMOLOGY
2012; 32 (3): 259-265
Giant cell arteritis (GCA) is an important cause of preventable blindness, most commonly due to anterior ischemic optic neuropathy. Ischemic tissue injury is the end result of a process that begins within the walls of susceptible arteries in which local dendritic cells (DCs) recruit and activate CD4 T cells that, in turn, direct the activity of effector macrophages. In response to the immune attack, the blood vessel forms lumen-stenosing intima. Multiple cascades of excessive T-cell reactivity contribute to the autoimmune features of giant cell arteritis with TH1 and TH17 immunity responsible for the early phase and TH1 immunity promoting chronic-smoldering inflammation. These cascades are only partially overlapping, supporting the concept that a multitude of instigators induce and sustain vascular inflammation. The artery actively participates in the abnormal immune response through endogenous immune sentinels, so-called vascular DCs embedded in the adventitia. Advancing age, the strongest of all risk factors for GCA, contributes to both, the dysfunction of the immune system and the vascular system. Expansion of the therapeutic armamentarium for GCA needs to focus on approaches that mitigate the impact of the aging artery and adapt to the needs of the immunosenescent host.
View details for DOI 10.1097/WNO.0b013e318268aa9b
View details for Web of Science ID 000308187800018
View details for PubMedID 22914691
CD8(+) CD45RA(+) CCR7(+) FOXP3(+) T Cells with Immunosuppressive Properties: A Novel Subset of Inducible Human Regulatory T Cells
JOURNAL OF IMMUNOLOGY
2012; 189 (5): 2118-2130
CD8 T cells stimulated with a suboptimal dose of anti-CD3 Abs (100 pg/ml) in the presence of IL-15 retain a naive phenotype with expression of CD45RA, CD28, CD27, and CCR7 but acquire new functions and differentiate into immunosuppressive T cells. CD8+CCR7+ regulatory T cells (Tregs) express FOXP3 and prevent CD4 T cells from responding to TCR stimulation and entering the cell cycle. Naive CD4 T cells are more susceptible to inhibition than memory cells. The suppressive activity of CD8+CCR7+ Tregs is not mediated by IL-10, TGF-?, CTLA-4, CCL4, or adenosine and relies on interference with very early steps of the TCR signaling cascade. Specifically, CD8+CCR7+ Tregs prevent TCR-induced phosphorylation of ZAP70 and dampen the rise of intracellular calcium in CD4 T cells. The inducibility of CD8+CCR7+ Tregs is correlated with the age of the individual with PBLs of donors older than 60 y yielding low numbers of FOXP3(low) CD8 Tregs. Loss of CD8+CCR7+ Tregs in the elderly host may be of relevance in the aging immune system as immunosenescence is associated with a state of chronic smoldering inflammation.
View details for DOI 10.4049/jimmunol.1200122
View details for Web of Science ID 000308083600009
View details for PubMedID 22821963
Chronic inflammation and aging: DNA damage tips the balance
CURRENT OPINION IN IMMUNOLOGY
2012; 24 (4): 488-493
The aged immune system, typically hyporesponsive to infection and vaccination, can be hyperresponsive in the context of inflammatory pathology. Here we review current work examining the mechanisms behind the amplified inflammatory profile of aged adaptive immunity, and the reciprocal relationship between chronic inflammation and immune aging. Aged hematopoietic stem cells are driven to differentiate following accumulated DNA damage, thus depleting the stem cell pool and increasing the number of damaged effector cells in the circulation. Chronic DNA damage responses in lymphocytes as well as senescent cells of other lineages initiate the production of inflammatory mediators. In addition, aged lymphocytes become less reliant on specific antigen for stimulation and more prone to activation through innate receptors. When these lymphocytes are exposed to inflammatory signals produced by senescent tissues, the bias toward inflammation exacerbates destruction without necessarily improving immunity.
View details for DOI 10.1016/j.coi.2012.04.003
View details for Web of Science ID 000308898700020
View details for PubMedID 22565047
K-RAS GTPase- and B-RAF kinase-mediated T-cell tolerance defects in rheumatoid arthritis
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2012; 109 (25): E1629-E1637
Autoantibodies to common autoantigens and neoantigens, such as IgG Fc and citrullinated peptides, are immunological hallmarks of rheumatoid arthritis (RA). We examined whether a failure in maintaining tolerance is mediated by defects in T-cell receptor activation threshold settings. RA T cells responded to stimulation with significantly higher ERK phosphorylation (P < 0.001). Gene expression arrays of ERK pathway members suggested a higher expression of KRAS and BRAF, which was confirmed by quantitative PCR (P = 0.003), Western blot, and flow cytometry (P < 0.01). Partial silencing of KRAS and BRAF lowered activation-induced phosphorylated ERK levels (P < 0.01). In individual cells, levels of these signaling molecules correlated with ERK phosphorylation, attesting that their concentrations are functionally important. In confocal studies, B-RAF/K-RAS clustering was increased in RA T cells 2 min after T-cell receptor stimulation (P < 0.001). Overexpression of B-RAF and K-RAS in normal CD4 T cells amplified polyclonal T-cell proliferation and facilitated responses to citrullinated peptides. We propose that increased expression of B-RAF and K-RAS lowers T-cell activation thresholds in RA T cells, enabling responses to autoantigens.
View details for DOI 10.1073/pnas.1117640109
View details for Web of Science ID 000306061400009
View details for PubMedID 22615393
Immune aging and autoimmunity
CELLULAR AND MOLECULAR LIFE SCIENCES
2012; 69 (10): 1615-1623
Age is an important risk for autoimmunity, and many autoimmune diseases preferentially occur in the second half of adulthood when immune competence has declined and thymic T cell generation has ceased. Many tolerance checkpoints have to fail for an autoimmune disease to develop, and several of those are susceptible to the immune aging process. Homeostatic T cell proliferation which is mainly responsible for T cell replenishment during adulthood can lead to the selection of T cells with increased affinity to self- or neoantigens and enhanced growth and survival properties. These cells can acquire a memory-like phenotype, in particular under lymphopenic conditions. Accumulation of end-differentiated effector T cells, either specific for self-antigen or for latent viruses, have a low activation threshold due to the expression of signaling and regulatory molecules and generate an inflammatory environment with their ability to be cytotoxic and to produce excessive amounts of cytokines and thereby inducing or amplifying autoimmune responses.
View details for DOI 10.1007/s00018-012-0970-0
View details for Web of Science ID 000303509800007
View details for PubMedID 22466672
Signal inhibition by the dual-specific phosphatase 4 impairs T cell-dependent B-cell responses with age
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2012; 109 (15): E879-E888
T cell-dependent B-cell responses decline with age, suggesting defective CD4 T-cell function. CD4 memory T cells from individuals older than 65 y displayed increased and sustained transcription of the dual-specific phosphatase 4 (DUSP4) that shortened expression of CD40-ligand (CD40L) and inducible T-cell costimulator (ICOS) (both P < 0.001) and decreased production of IL-4, IL-17A, and IL-21 (all P < 0.001) after in vitro activation. In vivo after influenza vaccination, activated CD4 T cells from elderly individuals had increased DUSP4 transcription (P = 0.002), which inversely correlated with the expression of CD40L (r = 0.65, P = 0.002), ICOS (r = 0.57, P = 0.008), and IL-4 (r = 0.66, P = 0.001). In CD4 KO mice reconstituted with DUSP4 OT-II T cells, DUSP4 had a negative effect on the expansion of antigen-specific B cells (P = 0.003) and the production of ova-specific antibodies (P = 0.03) after immunization. Silencing of DUSP4 in memory CD4 T cells improved CD40L (P < 0.001), IL-4 (P = 0.007), and IL-21 (P = 0.04) expression significantly more in the elderly than young adults. Consequently, the ability of CD4 memory T cells to support B-cell differentiation that was impaired in the elderly (P = 0.004) was restored. Our data suggest that increased DUSP4 expression in activated T cells in the elderly in part accounts for defective adaptive immune responses.
View details for DOI 10.1073/pnas.1109797109
View details for Web of Science ID 000302533500004
View details for PubMedID 22434910
Dampened ERK signaling in hematopoietic progenitor cells in rheumatoid arthritis
2012; 143 (1): 73-82
In rheumatoid arthritis (RA), hematopoietic progenitor cells (HPC) have age-inappropriate telomeric shortening suggesting premature senescence and possible restriction of proliferative capacity. In response to hematopoietic growth factors RA-derived CD34(+) HPC expanded significantly less than age-matched controls. Cell surface receptors for stem cell factor (SCF), Flt 3-Ligand, IL-3 and IL-6 were intact in RA HPC but the cells had lower transcript levels of cell cycle genes, compatible with insufficient signal strength in the ERK pathway. Cytokine-induced phosphorylation of ERK1/2 was diminished in RA HPC whereas phosphorylated STAT3 and STAT5 molecules accumulated to a similar extent as in controls. Confocal microscopy demonstrated that the membrane-proximal colocalization of K-Ras and B-Raf was less efficient in RA-derived CD34(+) cells. Thus, hyporesponsiveness of RA HPC to growth factors results from dampening of the ERK signaling pathways; with a defect localized in the very early steps of the ERK signaling cascade.
View details for DOI 10.1016/j.clim.2012.01.007
View details for Web of Science ID 000301908800010
View details for PubMedID 22342385
Mechanisms of immunosenescence: lessons from models of accelerated immune aging
YEAR IN IMMUNOLOGY
2012; 1247: 69-82
With increasing age, the ability of the adaptive immune system to respond to vaccines and to protect from infection declines. In parallel, the production of inflammatory mediators increases. While cross-sectional studies have been successful in defining age-dependent immunological phenotypes, studies of accelerated immune aging in human subpopulations have been instrumental in obtaining mechanistic insights. The immune system depends on its regenerative capacity; however, the T cell repertoire, once established, is relatively robust to aging and only decompensates when additionally stressed. Such stressors include chronic infections such as CMV and HIV, even when viral replication is controlled, and autoimmune diseases. Reduced regenerative capacity, chronic immune activation in the absence of cell exhaustion, T cell memory inflation, and accumulation of highly potent effector T cells in these patients synergize to develop an immune phenotype that is characteristic of the elderly. Studies of accelerated immune aging in autoimmune diseases have identified an unexpected link to chronic DNA damage responses that are known to be important in aging, but so far had not been implicated in immune aging.
View details for DOI 10.1111/j.1749-6632.2011.06297.x
View details for Web of Science ID 000305676600007
View details for PubMedID 22224726
Telomere dysfunction, autoimmunity and aging.
Aging and disease
2011; 2 (6): 524-537
Immune aging is associated with loss of critical immune functions, such as host protection from infection and malignancy. Unexpectedly, immunosenescence also renders the host susceptible to inflammation, which may translate into tissue-damaging disease as the senescent immune system loses its ability to maximize inflammatory protection while minimizing inflammatory injury. On the other hand, chronic inflammation associated with immune-mediated disease represents a profound stress factor for the immune system, affecting cellular turn-over, replication and exhaustion. Immune cell longevity is tightly connected to the functional integrity of telomeres which are regulated by cell multiplication, exposure to oxidative stress and DNA repair mechanisms. Lymphocytes are amongst the few cell types that can actively elongate telomeres through the action of telomerase. In patients with the autoimmune disease rheumatoid arthritis (RA), telomerase deficiency is associated with prematurity of immune aging. Patients with RA have other defects in DNA repair mechanisms, including the kinase Ataxia telangiectasia mutated (ATM), critically involved in the repair of DNA double strand breaks. ATM deficiency in RA shortens lymphocyte survival. Dynamics of telomeric length and structure are beginning to be understood and have distinct patterns in different autoimmune diseases, suggesting a multitude of molecular mechanisms defining the interface between chronic immune stimulation and progressive aging of the immune system.
View details for PubMedID 22396899
Finding Balance: T cell Regulatory Receptor Expression during Aging.
Aging and disease
2011; 2 (5): 398-413
Aging is associated with a variety of changes to immune responsiveness. Reduced protection against infection, reduced responses to vaccination and increased risk of autoimmunity are all hallmarks of advanced age. Here we consider how changes in the expression of regulatory receptors on the T cell surface contribute to altered immunity during aging.
View details for PubMedID 22396890
Magnetic Resonance Angiography in Extracranial Giant Cell Arteritis
JCR-JOURNAL OF CLINICAL RHEUMATOLOGY
2011; 17 (6): 306-310
Noninvasive diagnosis of giant cell arteritis (GCA) remains challenging, particularly with regard to evaluation of extracranial arterial disease.The objective of the study was to retrospectively review extracranial involvement in patients with GCA and/or polymyalgia rheumatica (PMR), evaluated with magnetic resonance imaging (MRI), especially 3-dimensional contrast-enhanced magnetic resonance angiography images of the aortic arch and its branches.Clinical information, biopsy status, and MRI examinations of 28 patients with GCA/PMR were reviewed. Patient images were mixed randomly with 20 normal control images and were independently reviewed by 2 radiologists. Interobserver agreement for detection of arterial stenosis was determined by the k coefficient.Both readers described vascular alterations in keeping with extracranial GCA in 19 of 28 patients (67%) with good interobserver agreement (k = 0.73) and with even higher agreement on diagnosing nonocclusive versus occlusive disease (k = 1.00). The most common lesions were bilateral axillary stenosis or obstructions, observed by both readers in 8 patients (28%). Among the 19 patients with magnetic resonance angiography lesions in the subclavian/axillary arteries, 12 (75%) had biopsy-proven GCA, but only 5 (41%) of these patients had clinical features of large artery disease.In our series review, MRI could provide accurate information on involvement of the aortic arch and its branches in extracranial GCA, depicting different degrees of stenosis. Our analysis also illustrates that occult large artery vasculitis should be considered in patients without biopsy-proven GCA, patients with classic GCA but without clinical signs of large artery disease, and in patients initially diagnosed as having PMR.
View details for DOI 10.1097/RHU.0b013e31822acec6
View details for Web of Science ID 000294483200003
View details for PubMedID 21869711
Inflammation and cardiac outcome
CURRENT OPINION IN INFECTIOUS DISEASES
2011; 24 (3): 259-264
Inflammation is a key component in cardiovascular disease. Controlling inflammatory events and their subsequent processes holds the potential for novel therapeutic treatment options. Cytokines are the propagators of inflammation. In this review we will discuss important cytokines including IL-6, TNF-?, MCP-1, fractalkine, M-CSF and GDF-15, and their effect on cardiac outcome.Recent studies have shed light on the role of IL-6 in cardiovascular disease. Long-term IL-6 levels are highly associated with coronary heart disease. Molecular studies indicate that a permanent prolongation of STAT signaling in cardiac myocytes might be a potential reason for the detrimental effects of IL-6. TNF-? was long considered to have detrimental effects on myocardial function but recent studies show cardioprotective mechanisms for TNF-?. Macrophage modulating cytokines emerge as interesting molecular targets to treat cardiovascular disease. Especially, the two different subtypes of monocytes, a pro-inflammatory and a reparative subset, and their different chemotactic properties might be possible drug targets. Finally, we discuss GDF-15, which emerges as a novel biomarker in cardiovascular disease reflecting information from several pathological pathways.Cytokines are the main proximal mediators of inflammation and hold the potential of being good molecular targets for novel treatment regimes. Cytokines might be valuable biomarkers, adding information about the pathologic pathways in cardiovascular disease.
View details for DOI 10.1097/QCO.0b013e328344f50f
View details for Web of Science ID 000289773600014
View details for PubMedID 21378564
Role of Increased Guanosine Triphosphate Cyclohydrolase-1 Expression and Tetrahydrobiopterin Levels upon T Cell Activation
JOURNAL OF BIOLOGICAL CHEMISTRY
2011; 286 (16): 13846-13851
Tetrahydrobiopterin (BH(4)) is an essential co-factor for the nitric-oxide (NO) synthases, and in its absence these enzymes produce superoxide (O(2)(·-)) rather than NO. The rate-limiting enzyme for BH(4) production is guanosine triphosphate cyclohydrolase-1 (GTPCH-1). Because endogenously produced NO affects T cell function, we sought to determine whether antigen stimulation affected T cell GTPCH-1 expression and ultimately BH(4) levels. Resting T cells had minimal expression of inducible NOS (NOS2), endothelial NOS (NOS3), and GTPCH-1 protein and nearly undetectable levels of BH(4). Anti-CD3 stimulation of T cells robustly stimulated the coordinated expression of NOS2, NOS3, and GTPCH-1 and markedly increased both GTPCH-1 activity and T cell BH(4) levels. The newly expressed GTPCH-1 was phosphorylated on serine 72 and pharmacological inhibition of casein kinase II reduced GTPCH-1 phosphorylation and blunted the increase in T cell BH(4). Inhibition of GTPCH-1 with diaminohydroxypyrimidine (1 mmol/liter) prevented T cell BH(4) accumulation, reduced NO production, and increased T cell O(2)(·-) production, due to both NOS2 and NOS3 uncoupling. GTPCH-1 inhibition also promoted TH(2) polarization in memory CD4 cells. Ovalbumin immunization of mice transgenic for an ovalbumin receptor (OT-II mice) confirmed a marked increase in T cell BH(4) in vivo. These studies identify a previously unidentified consequence of T cell activation, promoting BH(4) levels, NO production, and modulating T cell cytokine production.
View details for DOI 10.1074/jbc.M110.191023
View details for Web of Science ID 000289556200007
View details for PubMedID 21343293
Regulation of T cell receptor signaling by activation-induced zinc influx
JOURNAL OF EXPERIMENTAL MEDICINE
2011; 208 (4): 775-785
Zinc is a trace element that is essential for innate and adaptive immune responses. In addition to being a structural element of many proteins, zinc also functions as a neurotransmitter and an intracellular messenger. Temporal or spatial changes in bioavailable zinc may influence the activity of several enzymes, including kinases and phosphatases. We provide evidence that zinc functions as an ionic signaling molecule after T cell activation. Cytoplasmic zinc concentrations increased within 1 min after T cell receptor (TCR) triggering, in particular in the subsynaptic compartment. The increase depended on the extracellular zinc concentrations and was inhibited by silencing zinc transporter Zip6. Increased zinc influx reduced the recruitment of SHP-1 to the TCR activation complex, augmented ZAP70 phosphorylation and sustained calcium influx. By calibrating TCR activation thresholds, increased extracellular zinc bioavailability facilitated the induction of T cell proliferative responses to suboptimal stimuli.
View details for DOI 10.1084/jem.20100031
View details for Web of Science ID 000289404800012
View details for PubMedID 21422171
- Inflammation, Immunity, and Hypertension HYPERTENSION 2011; 57 (2): 132-140
Haematopoietic stem and progenitor cells in rheumatoid arthritis
2011; 50 (2): 252-260
RA is the prototypic chronic inflammatory disease, characterized by progressive articular cartilage and bone destruction. The systemic nature of RA is evidenced by the increased risk of atherosclerosis and lymphoproliferative disorders. Components of both the innate and adaptive immune system are implicated in the pathophysiology of the articular and extra-articular manifestations of the disease. A fundamental process in the onset of RA is the breakdown in self-tolerance. Accelerated ageing of immune cells (immunosenescence) appears to be a major mechanism favouring the disruption of tolerance. Telomere erosion, a hallmark of immunosenescence, is present in lymphoid (naïve and memory T cells) and myeloid (granulocytes) cells in RA. The premature ageing process also involves the haematopoietic stem and progenitor cells (CD34(+) HSPC), thus extending the RA immunopathogenesis to include early events in the shaping of the immune system. This review summarizes current concepts of HSPC ageing and its impact on immune regeneration, highlighting the phenotypic and functional similarities between elderly and RA HSPC.
View details for DOI 10.1093/rheumatology/keq298
View details for Web of Science ID 000286464100004
View details for PubMedID 20837497
Blocking the NOTCH Pathway Inhibits Vascular Inflammation in Large-Vessel Vasculitis
2011; 123 (3): 309-U180
Giant cell arteritis is a granulomatous vasculitis of the aorta and its branches that causes blindness, stroke, and aortic aneurysm. CD4 T cells are key pathogenic regulators, instructed by vessel wall dendritic cells to differentiate into vasculitic T cells. The unique pathways driving this dendritic cell-T-cell interaction are incompletely understood, but may provide novel therapeutic targets for a disease in which the only established therapy is long-term treatment with high doses of corticosteroids.Immunohistochemical and gene expression analyses of giant cell arteritis-affected temporal arteries revealed abundant expression of the NOTCH receptor and its ligands, Jagged1 and Delta1. Cleavage of the NOTCH intracellular domain in wall-infiltrating T cells indicated ongoing NOTCH pathway activation in large-vessel vasculitis. NOTCH activation did not occur in small-vessel vasculitis affecting branches of the vasa vasorum tree. We devised 2 strategies to block NOTCH pathway activation: ?-secretase inhibitor treatment, preventing nuclear translocation of the NOTCH intracellular domain, and competing for receptor-ligand interactions through excess soluble ligand, Jagged1-Fc. In a humanized mouse model, NOTCH pathway disruption had strong immunosuppressive effects, inhibiting T-cell activation in the early and established phases of vascular inflammation. NOTCH inhibition was particularly effective in downregulating Th17 responses, but also markedly suppressed Th1 responses.Blocking NOTCH signaling depleted T cells from the vascular infiltrates, implicating NOTCH- NOTCH ligand interactions in regulating T-cell retention and survival in vessel wall inflammation. Modulating the NOTCH signaling cascade emerges as a promising new strategy for immunosuppressive therapy of large-vessel vasculitis.
View details for DOI 10.1161/CIRCULATIONAHA.110.936203
View details for Web of Science ID 000286507800018
View details for PubMedID 21220737
Giant cell arteritis: immune and vascular aging as disease risk factors
ARTHRITIS RESEARCH & THERAPY
2011; 13 (4)
Susceptibility for giant cell arteritis increases with chronological age, in parallel with age-related restructuring of the immune system and age-induced remodeling of the vascular wall. Immunosenescence results in shrinkage of the naïve T-cell pool, contraction of T-cell diversity, and impairment of innate immunity. Aging of immunocompetent cells forces the host to take alternative routes for protective immunity and confers risk for pathogenic immunity that causes chronic inflammatory tissue damage. Dwindling immunocompetence is particularly relevant as the aging host is forced to cope with an ever growing infectious load. Immunosenescence coincides with vascular aging during which the arterial wall undergoes dramatic structural changes and medium and large arteries lose their pliability and elasticity. On the molecular level, elastic fibers deteriorate and matrix proteins accumulate biochemical modifications. Thus, the aging process impacts the two major biologic systems that liaise to promote giant cell arteritis; the immune system and the vessel wall niche.
View details for DOI 10.1186/ar3358
View details for Web of Science ID 000297150200044
View details for PubMedID 21861860
IFN-gamma and IL-17: the two faces of T-cell pathology in giant cell arteritis
CURRENT OPINION IN RHEUMATOLOGY
2011; 23 (1): 43-49
Granuloma formation in giant cell arteritis (GCA) emphasizes the role of adaptive immunity and highlights the role of antigen-specific T cells. Recent data demonstrate that at least two separate lineages of CD4 T cells participate in vascular inflammation, providing an important clue that multiple disease instigators may initiate pathogenic immunity.IFN-?-producing Th1 cells and IL-17-producing Th17 cells have been implicated in GCA. Patients with biopsy-positive GCA underwent two consecutive temporal artery biopsies, one prior to therapy and one while on corticosteroids. In untreated patients, Th1 and Th17 cells co-existed in the vascular lesions. Following therapy, Th17 cells were essentially lost, whereas Th1 cells persisted almost unaffected. In the peripheral blood of untreated patients Th17 frequencies were increased eight-fold, but normalized with therapy. Blood Th1 cells were doubled in frequency, independent of therapy. Corticosteroids functioned by selectively suppressing IL-1?, IL-6 and IL-23-releasing antigen-presenting cells (APCs), disrupting induction of Th17 cells.At least two distinct CD4 T-cell subsets promote vascular inflammation in GCA. In early disease, APCs promote differentiation of Th17 as well as Th1 cells. Chronic disease is characterized by persistent Th1-inducing signals, independent of IL-17-mediated inflammation. More than one disease instigator may trigger APCs to induce multiple T-cell lineages. Cocktails of therapies will be needed for appropriate disease control.
View details for DOI 10.1097/BOR.0b013e32833ee946
View details for Web of Science ID 000284868700008
View details for PubMedID 20827207
Inhibition and Genetic Ablation of the B7/CD28 T-Cell Costimulation Axis Prevents Experimental Hypertension
2010; 122 (24): 2529-2537
The pathogenesis of hypertension remains poorly understood, and treatment is often unsuccessful. Recent evidence suggests that the adaptive immune response plays an important role in this disease. Various hypertensive stimuli cause T-cell activation and infiltration into target organs such as the vessel and the kidney, which promotes vascular dysfunction and blood pressure elevation. Classically, T-cell activation requires T-cell receptor ligation and costimulation. The latter often involves interaction between B7 ligands (CD80 and CD86) on antigen-presenting cells with the T-cell coreceptor CD28. This study was therefore performed to examine the role of this pathway in hypertension.Angiotensin II-induced hypertension increased the presence of activated (CD86(+)) dendritic cells in secondary lymphatic tissues. Blockade of B7-dependent costimulation with CTLA4-Ig reduced both angiotensin II- and deoxycorticosterone acetate (DOCA)-salt-induced hypertension. Activation of circulating T cells, T-cell cytokine production, and vascular T-cell accumulation caused by these hypertensive stimuli were abrogated by CTLA4-Ig. Furthermore, in mice lacking B7 ligands, angiotensin II caused minimal blood pressure elevation and vascular inflammation, and these effects were restored by transplantation with wild-type bone marrow.T-cell costimulation via B7 ligands is essential for development of experimental hypertension, and inhibition of this process could have therapeutic benefit in the treatment of this disease.
View details for DOI 10.1161/CIRCULATIONAHA.109.930446
View details for Web of Science ID 000285243200011
View details for PubMedID 21126972
Statins reduce endothelial cell apoptosis via inhibition of TRAIL expression on activated CD4 T cells in acute coronary syndrome
2010; 213 (1): 33-39
Statins reduce cardiovascular-related morbidity and mortality, but their effects on inflammation in atherosclerosis are not fully understood. We investigated whether statins can modulate cytotoxic functions of CD4 T cells in acute coronary syndrome (ACS).Fresh CD4 T cells were isolated from 55 patients with ACS without statin treatment on admission and from 34 age-matched controls. CD4 T cells collected from ACS patients induced endothelial cell apoptosis significantly more than control T cells. The TNF-related apoptosis-inducing ligand (TRAIL) receptor DR5 was strongly upregulated on endothelial cells, and TRAIL-specific antibodies effectively blocked CD4 T cell-mediated apoptosis, indicating that T cell-mediated endothelial death was dependent on the TRAIL pathway. Expression of both the activating antigen CD69 and TRAIL was enhanced on ACS T cells. In in-vitro assays rosuvastatin, fluvastatin, and pitavastatin directly blocked CD4 T cell-mediated endothelial cell apoptosis and reduced T cell-expression of CD69 and TRAIL through TCR-induced Extracellar signal-Regulated Kinases (ERK) activation.Activated CD4 T cells expressing TRAIL are enriched in the blood of ACS patients and induce endothelial injury, which may contribute to the destabilization of the plaque. Early statin therapy may suppress T cell-mediated endothelial cell damage in atherosclerotic plaques and thus prevent cardiovascular events.
View details for DOI 10.1016/j.atherosclerosis.2010.03.034
View details for Web of Science ID 000283356400058
View details for PubMedID 20430391
Th17 Cells in Takayasu Arteritis
LIPPINCOTT WILLIAMS & WILKINS. 2010: E198-E198
View details for Web of Science ID 000283234800073
DNA-dependent protein kinase catalytic subunit mediates T-cell loss in rheumatoid arthritis
EMBO MOLECULAR MEDICINE
2010; 2 (10): 415-427
In the autoimmune syndrome rheumatoid arthritis (RA), T cells and T-cell precursors have age-inappropriate shortening of telomeres and accumulate deoxyribonucleic acid (DNA) double strand breaks. Whether damaged DNA elicits DNA repair activity and how this affects T-cell function and survival is unknown. Here, we report that naïve and resting T cells from RA patients are susceptible to undergo apoptosis. In such T cells, unrepaired DNA stimulates a p53-ataxia telangiectasia mutated-independent pathway involving the non-homologous-end-joining protein DNA-protein kinase catalytic subunit (DNA-PKcs). Upregulation of DNA-PKcs transcription, protein expression and phosphorylation in RA T cells co-occurs with diminished expression of the Ku70/80 heterodimer, limiting DNA repair capacity. Inhibition of DNA-PKcs kinase activity or gene silencing of DNA-PKcs protects RA T cells from apoptosis. DNA-PKcs induces T-cell death by activating the JNK pathway and upregulating the apoptogenic BH3-only proteins Bim and Bmf. In essence, in RA, the DNA-PKcs-JNK-Bim/Bmf axis transmits genotoxic stress into shortened survival of naïve resting T cells, imposing chronic proliferative turnover of the immune system and premature immunosenescence. Therapeutic blockade of the DNA-PK-dependent cell-death machinery may rejuvenate the immune system in RA.
View details for DOI 10.1002/emmm.201000096
View details for Web of Science ID 000283891400005
View details for PubMedID 20878914
Central and Peripheral Mechanisms of T-Lymphocyte Activation and Vascular Inflammation Produced by Angiotensin II-Induced Hypertension
2010; 107 (2): 263-U186
We have previously found that T lymphocytes are essential for development of angiotensin II-induced hypertension; however, the mechanisms responsible for T-cell activation in hypertension remain undefined.We sought to study the roles of the CNS and pressure elevation in T-cell activation and vascular inflammation caused by angiotensin II.To prevent the central actions of angiotensin II, we created anteroventral third cerebral ventricle (AV3V) lesions in mice. The elevation in blood pressure in response to angiotensin II was virtually eliminated by AV3V lesions, as was activation of circulating T cells and the vascular infiltration of leukocytes. In contrast, AV3V lesioning did not prevent the hypertension and T-cell activation caused by the peripheral acting agonist norepinephrine. To determine whether T-cell activation and vascular inflammation are attributable to central influences or are mediated by blood pressure elevation, we administered hydralazine (250 mg/L) in the drinking water. Hydralazine prevented the hypertension and abrogated the increase in circulating activated T cells and vascular infiltration of leukocytes caused by angiotensin II.We conclude that the central and pressor effects of angiotensin II are critical for T-cell activation and development of vascular inflammation. These findings also support a feed-forward mechanism in which modest degrees of blood pressure elevation lead to T-cell activation, which in turn promotes inflammation and further raises blood pressure, leading to severe hypertension.
View details for DOI 10.1161/CIRCRESAHA.110.217299
View details for Web of Science ID 000280201200013
View details for PubMedID 20558826
Immune Aging and Rheumatoid Arthritis
RHEUMATIC DISEASE CLINICS OF NORTH AMERICA
2010; 36 (2): 297-?
Immunologic models of rheumatoid arthritis (RA) have to take into account that the disease occurs at an age when immunocompetence is declining and in a host whose immune system shows evidence of accelerated immune aging. By several immune aging biomarkers, the immune system in patients with RA is prematurely aged by more than 20 years. One major pathogenetic mechanism is a defect in telomere maintenance and DNA repair that causes accelerated cell death. These findings in RA are reminiscent of murine autoimmunity models, in which lymphopenia was identified as a major risk factor for autoimmunity. Progress in the understanding of how accelerated immune aging is pathogenetically involved in RA may allow development of new therapeutic approaches that go beyond the use of anti-inflammatory agents and eventually could open new avenues for preventive intervention.
View details for DOI 10.1016/j.rdc.2010.03.001
View details for Web of Science ID 000279254800006
View details for PubMedID 20510235
Promoter choice and translational repression determine cell type-specific cell surface density of the inhibitory receptor CD85j expressed on different hematopoietic lineages
2010; 115 (16): 3278-3286
CD85j (ILT2/LILRB1/LIR-1) is an inhibitory receptor that recognizes major histocompatibility complex (MHC) class Ia and Ib alleles that are widely expressed on all cell types. On ligand recognition, CD85j diminishes kinase activity by recruiting phosphatases to motifs within its cytoplasmic domain. Within the hematopoietic system, CD85j is expressed with cell-specific patterns and cell surface densities that reflect the different roles of cell contact-mediated inhibition in these lineages. While monocytes ubiquitously have high cell surface expression, B lymphocytes start to express CD85j at intermediate levels during early B-cell maturation and natural killer (NK) cells and T cells exhibit a low level of expression on only a subset of cells. The cell-specific expression pattern is accomplished by 2 complementing but not independent mechanisms. Lymphocytes and monocytes use distinct promoters to drive CD85j expression. The lymphocyte promoter maps 13 kilobases (kb) upstream of the monocyte promoter; its use results in the inclusion of a distant exon into the 5'-untranslated region. A short sequence stretch within this exon has the unique function of repressing CD85j protein translation and is responsible for the subdued expression in lymphocytes. These cell-specific mechanisms allow tailoring of CD85j levels to the distinct roles it plays in different hematopoietic lineages.
View details for DOI 10.1182/blood-2009-09-243493
View details for Web of Science ID 000276956500014
View details for PubMedID 20194892
Insufficient Deactivation of the Protein Tyrosine Kinase Lck Amplifies T-Cell Responsiveness in Acute Coronary Syndrome
2010; 106 (4): 769-U269
In the vulnerable atherosclerotic plaque, T cells may destabilize the tissue structure through direct cell-injurious effector functions. T cells transmit environmental signals, such as recognition of antigen, into cellular responses through regulated phosphorylation of cytoplasmic proteins, with the Src family kinase Lck (lymphocyte-specific protein tyrosine kinase) in critical membrane-proximal position of the T-cell receptor (TCR) signaling cascade. The balance between protein phosphorylation and dephosphorylation defines the signal transduction threshold and determines appropriate T-cell responses.We have examined whether abnormal calibration of intracellular signaling pathways renders acute coronary syndrome (ACS) patients susceptible to disproportionate T-cell responses.Intracellular signaling cascades were quantified in CD4 T cells from ACS patients and control individuals after stimulation with major histocompatibility complex class II-superantigen complexes. ACS T cells mobilized more intracellular calcium and accumulated higher levels of phosphotyrosine than control T cells. Proximal steps in TCR signaling, such as recruitment of ZAP-70 and clustering of TCR complexes in the immune synapse, were abnormally enhanced in ACS T cells. Acceleration of the signaling cascade derived from a proximal defect in ACS T cells, which failed to phosphorylate Lck at Tyr505, extending activation of the Src kinase. Abnormalities in TCR signaling did not correlate with systemic inflammation as measured by C-reactive protein.An intrinsic abnormality in the signaling machinery of ACS T cells resulting in the accumulation of active Lck lowers the TCR threshold and renders lymphocytes hyperreactive and capable of unwanted immune responses.
View details for DOI 10.1161/CIRCRESAHA.109.206052
View details for Web of Science ID 000275190500018
View details for PubMedID 20035083
Th17 and Th1 T-Cell Responses in Giant Cell Arteritis
2010; 121 (7): 906-U107
In giant cell arteritis (GCA), vasculitic damage of the aorta and its branches is combined with a syndrome of intense systemic inflammation. Therapeutically, glucocorticoids remain the gold standard because they promptly and effectively suppress acute manifestations; however, they fail to eradicate vessel wall infiltrates. The effects of glucocorticoids on the systemic and vascular components of GCA are not understood.The immunoprofile of untreated and glucocorticoid-treated GCA was examined in peripheral blood and temporal artery biopsies with protein quantification assays, flow cytometry, quantitative real-time polymerase chain reaction, and immunohistochemistry. Plasma interferon-gamma and interleukin (IL)-17 and frequencies of interferon-gamma-producing and IL-17-producing T cells were markedly elevated before therapy. Glucocorticoid treatment suppressed the Th17 but not the Th1 arm in the blood and the vascular lesions. Analysis of monocytes/macrophages in the circulation and in temporal arteries revealed glucocorticoid-mediated suppression of Th17-promoting cytokines (IL-1beta, IL-6, and IL-23) but sparing of Th1-promoting cytokines (IL-12). In human artery-severe combined immunodeficiency mouse chimeras, in which patient-derived T cells cause inflammation of engrafted human temporal arteries, glucocorticoids were similarly selective in inhibiting Th17 cells and leaving Th1 cells unaffected.Two pathogenic pathways mediated by Th17 and Th1 cells contribute to the systemic and vascular manifestations of GCA. IL-17-producing Th17 cells are sensitive to glucocorticoid-mediated suppression, but interferon-gamma-producing Th1 responses persist in treated patients. Targeting steroid-resistant Th1 responses will be necessary to resolve chronic smoldering vasculitis. Monitoring Th17 and Th1 frequencies can aid in assessing disease activity in GCA.
View details for DOI 10.1161/CIRCULATIONAHA.109.872903
View details for Web of Science ID 000274797500011
View details for PubMedID 20142449
Induction of Hypertension and Peripheral Inflammation by Reduction of Extracellular Superoxide Dismutase in the Central Nervous System
2010; 55 (2): 277-U143
The circumventricular organs (CVOs) lack a well-formed blood-brain barrier and produce superoxide in response to angiotensin II and other hypertensive stimuli. This increase in central superoxide has been implicated in the regulation of blood pressure. The extracellular superoxide dismutase (SOD3) is highly expressed in cells associated with CVOs and particularly with tanycytes lining this region. To understand the role of SOD3 in the CVOs in blood pressure regulation, we performed intracerebroventricular injection an adenovirus encoding Cre-recombinase (5x10(8) particles per milliliter) in mice with loxP sites flanking the SOD3 coding region (SOD3(loxp/loxp) mice). An adenovirus encoding red-fluorescent protein was injected as a control. Deletion of CVO SOD3 increased baseline blood pressure modestly and markedly augmented the hypertensive response to low-dose angiotensin II (140 ng/kg per day), whereas intracerebroventricular injection of adenovirus encoding red-fluorescent protein had minimal effects on these parameters. Adenovirus encoding Cre-recombinase-treated mice exhibited increased sympathetic modulation of heart rate and blood pressure variability, increased vascular superoxide production, and T-cell activation as characterized by increased circulating CD69(+)/CD3(+) cells. Deletion of CVO SOD3 also markedly increased vascular T-cell and leukocyte infiltration caused by angiotensin II. We conclude that SOD3 in the CVO plays a critical role in the regulation of blood pressure, and its loss promotes T-cell activation and vascular inflammation, in part by modulating sympathetic outflow. These findings provide insight into how central signals produce vascular inflammation in response to hypertensive stimuli, such as angiotensin II.
View details for DOI 10.1161/HYPERTENSIONAHA.109.142646
View details for Web of Science ID 000273802500018
View details for PubMedID 20008675
Telomeres and Immunological Diseases of Aging
2010; 56 (4): 390-403
A defining feature of the eukaryotic genome is the presence of linear chromosomes. This arrangement, however, poses several challenges with regard to chromosomal replication and maintenance. To prevent the loss of coding sequences and to suppress gross chromosomal rearrangements, linear chromosomes are capped by repetitive nucleoprotein structures, called telomeres. Each cell division results in a progressive shortening of telomeres that, below a certain threshold, promotes genome instability, senescence, and apoptosis. Telomeric erosion, maintenance, and repair take center stage in determining cell fate. Cells of the immune system are under enormous proliferative demand, stressing telomeric intactness. Lymphocytes are capable of upregulating telomerase, an enzyme that can elongate telomeric sequences and, thus, prolong cellular lifespan. Therefore, telomere dynamics are critical in preserving immune function and have become a focus for studies of immunosenescence and autoimmunity. In this review, we describe the role of telomeric nucleoproteins in shaping telomere architecture and in suppressing DNA damage responses. We summarize new insights into the regulation of telomerase activity, hereditary disorders associated with telomere dysfunction, the role of telomere loss in immune aging, and the impact of telomere dysfunction in chronic inflammatory disease.
View details for DOI 10.1159/000268620
View details for Web of Science ID 000278673900005
View details for PubMedID 20016137
Dendritic cells in atherosclerotic disease
2010; 134 (1): 25-32
Atherosclerosis has been considered a syndrome of dysregulated lipid storage until recent evidence has emphasized the critical contribution of the immune system. Dendritic cells (DC) are positioned at the interface of the innate and adaptive immune system. Recognition of danger signals in atheromas leads to DC activation. Activated DC regulate effector T cells which can kill plaque-resident cells and damage the plaque structure. Two types of DC have been identified in atherosclerotic lesions; classical myeloid DC (mDC) which mainly recognize bacterial signatures and plasmacytoid DC (pDC) which specialize in sensing viral fragments and have the unique potential of producing large amounts of type I interferon (IFN). In human atheromas, type I IFN upregulates expression of the cytotoxic molecule TRAIL which leads to apoptosis of plaque-resident cells. This review will elucidate the role of DC in atherogenesis and particularly in plaque rupture, the underlying pathophysiologic cause of myocardial infarction.
View details for DOI 10.1016/j.clim.2009.05.006
View details for Web of Science ID 000273696600003
View details for PubMedID 19520615
ERK-Dependent T Cell Receptor Threshold Calibration in Rheumatoid Arthritis
JOURNAL OF IMMUNOLOGY
2009; 183 (12): 8258-8267
Immune responses to citrullinated neoantigens and clinical efficacy of costimulation blockade indicate a general defect in maintaining T cell tolerance in rheumatoid arthritis (RA). To examine whether TCR threshold calibration contributes to disease pathogenesis, signaling in RA T cells was quantified. RA patients had a selective increase in ERK phosphorylation compared with demographically matched controls due to a mechanism distal of Ras activation. Increased ERK responses included naive and memory CD4 and CD8 T cells and did not correlate with disease activity. The augmented ERK activity delayed SHP-1 recruitment to the TCR synapse and sustained TCR-induced Zap70 and NF-kappaB signaling, facilitating responses to suboptimal stimulation. Increased responsiveness of the ERK pathway was also a characteristic finding in the SKG mouse model of RA where it preceded clinical symptoms. Treatment with subtherapeutic doses of a MEK-1/2 inhibitor delayed arthritis onset and reduced severity, suggesting that increased ERK phosphorylation predisposes for autoimmunity and can be targeted to prevent disease.
View details for DOI 10.4049/jimmunol.0901784
View details for Web of Science ID 000272861300071
View details for PubMedID 20007589
Epigenetic regulation of killer immunoglobulin-like receptor expression in T cells
2009; 114 (16): 3422-3430
With increasing age, T cells gain expression of killer immunoglobulin-like receptors (KIRs) that transmit negative signals and dampen the immune response. KIR expression is induced in CD4 and CD8 T cells by CpG DNA demethylation suggesting epigenetic control. To define the mechanisms that underlie the age-associated preferential KIR expression in CD8 T cells, we examined KIR2DL3 promoter methylation patterns. With age, CD8 T cells developed a patchy and stochastic promoter demethylation even in cells that did not express the KIR2DL3-encoded CD158b protein; complete demethylation of the minimal KIR2DL3 promoter was characteristic for CD158b-expressing cells. In contrast, the promoter in CD4 T cells was fully methylated irrespective of age. The selectivity for CD8 T cells correlated with lower DNMT1 recruitment to the KIR2DL3 promoter which further diminished with age. In contrast, binding of the polycomb protein EZH2 known to be involved in DNMT1 recruitment was not different. Our data suggest that CD8 T cells endure increasing displacement of DNMT1 from the KIR promoter with age, possibly because of an active histone signature. The ensuing partial demethylation lowers the threshold for transcriptional activation and renders CD8 T cells more susceptible to express KIR, thereby contributing to the immune defect in the elderly.
View details for DOI 10.1182/blood-2009-01-200170
View details for Web of Science ID 000270834500012
View details for PubMedID 19628706
Rejuvenating the immune system in rheumatoid arthritis
NATURE REVIEWS RHEUMATOLOGY
2009; 5 (10): 583-588
In rheumatoid arthritis (RA), the aging process of the immune system is accelerated. Formerly, this phenomenon was suspected to be a consequence of chronic inflammatory activity. However, newer data strongly suggest that deficiencies in maintaining telomeres and overall DNA stability cause excessive apoptosis of RA T cells, imposing proliferative pressure and premature aging on the system. Already during the early stages of their life cycle, and long before they participate in the inflammatory process, RA T cells are lost owing to increased apoptotic susceptibility. A search for underlying mechanisms has led to the discovery of defective pathways of repairing broken DNA and elongating and protecting telomeric sequences at the chromosomal ends. Two enzymatic machineries devoted to DNA repair and maintenance have been implicated. RA T cells fail to induce sufficient amounts of the telomeric repair enzyme telomerase, leaving telomeric ends uncapped and thus susceptible to damage. Of equal importance, RA T cells produce low levels of the DNA repair enzyme ataxia telangiectasia mutated and the complex of nucleoproteins that sense and fix DNA double-strand breaks. The inability to repair damaged DNA renders naive T cells vulnerable to apoptosis, exhausts T-cell regeneration and reshapes the T cell repertoire. Therapeutic attempts to reset the immune systems of patients with RA and prevent premature immunosenescence should include restoration of DNA repair capability.
View details for DOI 10.1038/nrrheum.2009.180
View details for Web of Science ID 000270417600013
View details for PubMedID 19798035
Treating autoimmune disease by targeting CD8(+) T suppressor cells
EXPERT OPINION ON BIOLOGICAL THERAPY
2009; 9 (8): 951-965
Current treatments for autoimmune disease are hampered by the non-specificity of immunomodulatory interventions, having to accept broad suppression of immunoresponsiveness with potentially serious side effects, such as infection or malignancy. The development of antigen-specific approaches, downregulating pathogenic immune responses while maintaining protective immunity, would be a major step forward. One possible approach involves the targeting of physiological regulatory mechanisms, such as inhibitory CD8 T cells that are now recognized to fine-tune many aspects of immune responses. CD8 T suppressor (Ts) cells may directly inhibit other T cells or condition antigen-presenting cells in such a way that immune amplification steps are dampened. The promise of CD8 Ts cells lies in their potential to disrupt host-injurious immune responses in a targeted fashion. For therapeutic purposes, such CD8 Ts cells could either be generated in vitro and transferred into the host or their numbers and activity could be modulated by treating the patient with established or novel immunomodulators. Emerging evidence shows that several subsets of CD8 Ts cells exist. While there is still considerable uncertainty about the molecular mechanisms through which CD8 Ts cells can reset immune responses to protect the host, their potential diagnostic and therapeutic use is intriguing and has generated renewed interest.
View details for DOI 10.1517/14712590903020759
View details for Web of Science ID 000268660100002
View details for PubMedID 19522557
Clinicopathologic Correlations in Giant Cell Arteritis A Retrospective Study of 107 Cases
2009; 116 (8): 1574-1580
To correlate the pathologic findings of temporal artery biopsies in patients clinically defined as positive, presumed, or negative for giant cell arteritis (GCA).Retrospective case series.Patients evaluated for GCA.Temporal artery biopsies examined between 1989 and 2007 were studied. Clinical information and residual tissue for immunohistochemical staining was identified in 107 patients. Clinical information was used to make a diagnosis of "positive," "presumed," or "negative" GCA. The biopsies were reviewed in a masked fashion and classified as "positive," "indeterminate," or "negative" based on published, classic pathologic diagnosis (CPD) criteria. All biopsies were immunostained for CD3 and CD68 and graded as "negative," "mildly" (+), "moderately" (++), or "markedly" (+++) positive. Clinical and pathologic results were correlated and a modified pathologic diagnosis classification (MPD) scheme was developed. The modified scheme was compared in a masked fashion with the final clinical diagnosis and positive and negative predictive values (PVs) were calculated.Pathologic diagnosis and final clinical diagnosis.Using the MPD classification, there were 25%, 16%, and 61% positive, indeterminate, and negative biopsies, respectively. There was excellent correlation between the modified pathologic criteria and final clinical diagnosis (correlation coefficient 0.997; P<0.0001; kappa = 0.81). The positive PVs for CPD and MPD were 85% and 96%, respectively. The negative PVs for CPD and MPD were 64% and 61%, respectively. Positive and negative biopsies strongly correlated with clinical diagnoses of positive and negative for GCA, respectively, whereas indeterminate cases moderately correlated with presumed GCA. The diagnosis did not change from the original biopsy in 11 patients who had a second biopsy. Immunostaining for CD 68 was helpful in several indeterminate cases.We recommend using the modified histologic classification of temporal artery biopsies. There are indeterminate cases that cannot be further defined using current pathologic classification criteria. A second biopsy has very limited value. Immunostaining for CD68 may be helpful in indeterminate cases, although the diagnosis in these cases is based on clinical judgment.
View details for DOI 10.1016/j.ophtha.2009.02.027
View details for Web of Science ID 000268710200025
View details for PubMedID 19500846
Deficiency of the DNA repair enzyme ATM in rheumatoid arthritis
JOURNAL OF EXPERIMENTAL MEDICINE
2009; 206 (6): 1435-1449
In rheumatoid arthritis (RA), dysfunctional T cells sustain chronic inflammatory immune responses in the synovium. Even unprimed T cells are under excessive replication pressure, suggesting an intrinsic defect in T cell regeneration. In naive CD4 CD45RA(+) T cells from RA patients, DNA damage load and apoptosis rates were markedly higher than in controls; repair of radiation-induced DNA breaks was blunted and delayed. DNA damage was highest in newly diagnosed untreated patients. RA T cells failed to produce sufficient transcripts and protein of the DNA repair kinase ataxia telangiectasia (AT) mutated (ATM). NBS1, RAD50, MRE11, and p53 were also repressed. ATM knockdown mimicked the biological effects characteristic for RA T cells. Conversely, ATM overexpression reconstituted DNA repair capabilities, response patterns to genotoxic stress, and production of MRE11 complex components and rescued RA T cells from apoptotic death. In conclusion, ATM deficiency in RA disrupts DNA repair and renders T cells sensitive to apoptosis. Apoptotic attrition of naive T cells imposes lymphopenia-induced proliferation, leading to premature immunosenescence and an autoimmune-biased T cell repertoire. Restoration of DNA repair mechanisms emerges as an important therapeutic target in RA.
View details for DOI 10.1084/jem.20082251
View details for Web of Science ID 000267133700020
View details for PubMedID 19451263
Telomerase insufficiency in rheumatoid arthritis
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2009; 106 (11): 4360-4365
In rheumatoid arthritis (RA), chronically stimulated T lymphocytes sustain tissue-destructive joint inflammation. Both naïve and memory T cells in RA are prematurely aged with accelerated loss of telomeres suggesting excessive proliferative pressure or inadequate telomeric maintenance. Upon stimulation, RA naïve CD4 T cells are defective in up-regulating telomerase activity (P < 0.0001) due to insufficient induction of the telomerase component human telomerase reverse transcriptase (hTERT); T cell activation and cell cycle progression are intact. Telomerase insufficiency does not affect memory T cells or CD34 hematopoietic stem cells and is present in untreated patients and independent from disease activity. Knockdown of hTERT in primary human T cells increases apoptotic propensity (P = 0.00005) and limits clonal burst (P = 0.0001) revealing a direct involvement of telomerase in T cell fate decisions. Naïve RA CD4 T cells stimulated through the T cell receptor are highly susceptible to apoptosis, expanding to smaller clonal size. Overexpression of ectopic hTERT in naïve RA T cells conveys apoptotic resistance (P = 0.008) and restores proliferative expansion (P < 0.0001). Telomerase insufficiency in RA results in excessive T cell loss, undermining homeostatic control of the naive T cell compartment and setting the stage for lymphopenia-induced T cell repertoire remodeling. Restoring defective telomerase activity emerges as a therapeutic target in resetting immune abnormalities in RA.
View details for DOI 10.1073/pnas.0811332106
View details for Web of Science ID 000264278800056
View details for PubMedID 19255426
Pathogenesis of medium- and large-vessel vasculitis
ZEITSCHRIFT FUR RHEUMATOLOGIE
2009; 68 (2): 100-?
Giant cell arteritis (GCA), is a systemic vasculitis which preferentially targets large and medium branches of the upper-body aorta. Typical clinical manifestations result from arterial stenosis/occlusion causing blindness, stroke and aortic arch syndrome. Aortic involvement leads to dissection and aneurysm. On the cellular and molecular level, GCA is a sequel of abnormal innate and adaptive immune responses that occur in the specialized tissue niche of the arterial wall. Based on recent pathogenic studies, a novel disease model for GCA is emerging. It is now understood that the series of pathogenic events begins with dendritic cells (DC) indigenous to the artery's outer wall, leading to inflammatory vasculopathy. Placed close to the vasa vasorum, vascular DC are highly sensitive in recognizing pathogen-associated motifs assigning immune monitoring functions to blood vessels. Thus the large vessels are actively involved in immune monitoring. Each vascular territory expresses a unique profile of pathogen-sensing receptors, emphasizing functional diversity amongst structurally similar arteries. Innate immune stimulators can transform vascular DC into efficient antigen-presenting cells, attracting, activating, and instructing T lymphocytes to acquire tissue-invasive features. Macrophages provide critical tissue-damaging effector functions, directly injuring wall-residing cells and promoting a remodeling process that leads to intimal hyperplasia and luminal occlusion. Novel diagnostic and therapeutic approaches to GCA need to focus on the key position of vascular DC and the signals that break the immunoprivileged state of the vessel wall.
View details for DOI 10.1007/s00393-008-0374-6
View details for Web of Science ID 000266196500002
View details for PubMedID 19224227
Toll-Like Receptors 4 and 5 Induce Distinct Types of Vasculitis
2009; 104 (4): 488-U139
Large vessel vasculitides, such as Takayasu arteritis and giant cell arteritis, affect vital arteries and cause clinical complications by either luminal occlusion or vessel wall destruction. Inflammatory infiltrates, often with granulomatous arrangements, are distributed as a panarteritis throughout all of the artery's wall layers or cluster in the adventitia as a perivasculitis. Factors determining the architecture and compartmentalization of vasculitis are unknown. Human macrovessels are populated by indigenous dendritic cells (DCs) positioned in the adventitia. Herein, we report that these vascular DCs sense bacterial pathogens and regulate the patterning of the emerging arteritis. In human temporal artery-SCID chimeras, lipopolysaccharides stimulating Toll-like receptor (TLR)4 and flagellin stimulating TLR5 trigger vascular DCs and induce T-cell recruitment and activation. However, the architecture of the evolving inflammation is ligand-specific; TLR4 ligands cause transmural panarteritis and TLR5 ligands promote adventitial perivasculitis. Underlying mechanisms involve selective recruitment of functional T cell subsets. Specifically, TLR4-mediated DC stimulation markedly enhances production of the chemokine CCL20, biasing recruitment toward CCL20-responsive CCR6(+) T cells. In adoptive transfer experiments, CCR6(+) T cells produce an arteritis pattern with media-invasive T cells damaging vascular smooth muscle cells. Also, CCR6(+) T cells dominate the vasculitic infiltrates in patients with panarteritic giant cell arteritis. Thus, depending on the original danger signal, vascular DCs edit the emerging immune response by differentially recruiting specialized T effector cells and direct the disease process toward distinct types of vasculitis.
View details for DOI 10.1161/CIRCRESAHA.108.185777
View details for Web of Science ID 000263771600011
View details for PubMedID 19150884
Regulation of T-cell function by endogenously produced angiotensin II
AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY
2009; 296 (2): R208-R216
The adaptive immune response and, in particular, T cells have been shown to be important in the genesis of hypertension. In the present study, we sought to determine how the interplay between ANG II, NADPH oxidase, and reactive oxygen species modulates T cell activation and ultimately causes hypertension. We determined that T cells express angiotensinogen, the angiotensin I-converting enzyme, and renin and produce physiological levels of ANG II. AT1 receptors were primarily expressed intracellularly, and endogenously produced ANG II increased T-cell activation, expression of tissue homing markers, and production of the cytokine TNF-alpha. Inhibition of T-cell ACE reduced TNF-alpha production, indicating endogenously produced ANG II has a regulatory role in this process. Studies with specific antagonists and T cells from AT1R and AT2R-deficient mice indicated that both receptor subtypes contribute to TNF-alpha production. We found that superoxide was a critical mediator of T-cell TNF-alpha production, as this was significantly inhibited by polyethylene glycol (PEG)-SOD, but not PEG-catalase. Thus, T cells contain an endogenous renin-angiotensin system that modulates T-cell function, NADPH oxidase activity, and production of superoxide that, in turn, modulates TNF-alpha production. These findings contribute to our understanding of how ANG II and T cells enhance inflammation in cardiovascular disease.
View details for DOI 10.1152/ajpregu.90521.2008
View details for Web of Science ID 000262781200003
View details for PubMedID 19073907
Developments in the scientific understanding of rheumatoid arthritis
ARTHRITIS RESEARCH & THERAPY
2009; 11 (5)
Rheumatoid arthritis (RA) is recognized to be an autoimmune disease that causes preclinical systemic abnormalities and eventually leads to synovial inflammation and destruction of the joint architecture. Recently identified genetic risk factors and novel insights from animal models of spontaneous arthritis have lent support to the concept that thymic selection of an autoreactive T-cell repertoire is an important risk factor for this disease. With advancing age, defects in the homeostatic control of the T-cell pool and in the setting of signaling thresholds lead to the accumulation of pro-inflammatory T-effector cell populations and loss of tolerance to neo-antigens, such as citrullinated peptides. As the breakdown of tolerance to modified self-antigens can precede synovitis by decades, repair of homeostatic defects may open a unique window of opportunity for preventive interventions in RA. The end result of RA, destruction of cartilage and bone, appears to be driven by cytokine- and cell contact-induced activation of synoviocytes and monocytic cells, some of which differentiate into tissue-destructive osteoclasts. Targeting mediators involved in this process has greatly improved the management of this chronic inflammatory syndrome.
View details for DOI 10.1186/ar2758
View details for Web of Science ID 000273338400016
View details for PubMedID 19835638
Vascular damage in giant cell arteritis
2009; 42 (7): 596-604
Immune-mediated damage to medium-sized arteries results in wall remodeling with intimal hyperplasia, luminal stenosis and tissue ischemia. In the case of the aorta, vasculitis may result in dissection, aneurysm or rupture. The response-to-injury program of the blood vessel is a concerted action between the immune system and wall-resident cells, involving the release of growth and angiogenic factors from macrophages and giant cells and the migration and hyperproliferation of vascular smooth muscle cells. Innate immune cells, specifically, dendritic cells (DC) positioned in the vessel wall, have been implicated in the earliest steps of vasculitis. Pathogen-derived molecular patterns are capable of activating vascular DC and initiating adaptive immune responses. The pattern of the emerging vessel wall inflammation is ultimately determined by the initial insult. Ligands to toll-like receptor (TLR) 4, such as lipopolysaccharides, facilitate the recruitment of CD4 T cells that invade deep into the wall and distribute in a panarteritic pattern. Conversely, ligands for TLR5 condition vascular DC to support perivasculitic infiltrates. In essence, both innate and adaptive immune reactions collaborate to render the arterial wall susceptible to inflammatory damage. Unique features of the tissue microenvironment, including specialized DC, shape the course of the inflammatory response. Differences in vascular damage pattern encountered in different patients may relate to distinct instigators of vasculitis.
View details for DOI 10.1080/08916930903002495
View details for Web of Science ID 000270287500006
View details for PubMedID 19657775
Age-Dependent Signature of Metallothionein Expression in Primary CD4 T Cell Responses Is Due to Sustained Zinc Signaling
2008; 11 (6): 1001-1011
The ability to mount adaptive immune responses to vaccinations and viral infections declines with increasing age. To identify mechanisms leading to immunosenescence, primary CD4 T cell responses were examined in 60- to 75-year-old individuals lacking overt functional defects. Transcriptome analysis indicated a selective defect in zinc homeostasis. CD4 T cell activation was associated with zinc influx via the zinc transporter Zip6, leading to increased free cytoplasmic zinc and activation of negative feedback loops, including the induction of zinc-binding metallothioneins. In young adults, activation-induced cytoplasmic zinc concentrations declined after 2 days to below prestimulation levels. In contrast, activated naïve CD4 T cells from older individuals failed to downregulate cytoplasmic zinc, resulting in excessive induction of metallothioneins. Activation-induced metallothioneins regulated the redox state in activated T cells and accounted for an increased proliferation of old CD4 T cells, suggesting that regulation of T cell zinc homeostasis functions as a compensatory mechanism to preserve the replicative potential of naïve CD4 T cells with age.
View details for DOI 10.1089/rej.2008.0747
View details for Web of Science ID 000262886400003
View details for PubMedID 19072254
Inhibitory CD8(+) T cells in autoimmune disease
2008; 69 (11): 781-789
Rheumatologists have long been focused on developing novel immunotherapeutic agents to manage such prototypic autoimmune diseases as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). The ultimate challenge in providing immunosuppressive treatment for patients with RA and SLE has derived from the dilemma that both protective and harmful immune responses result from adaptive immune responses, mediated by highly diverse, antigen-specific T and B cells endowed with powerful effector functions and the ability for long-lasting memory. As regulatory/suppressor T cells can suppress immunity against any antigen, including self-antigens, they emerge as an ideal therapeutic target. Several distinct subtypes of CD8(+) suppressor cells (Ts) have been described that could find application in treating RA or SLE. In a xenograft model of human synovium, CD8(+)CD28(-)CD56(+) T cells effectively suppressed rheumatoid inflammation. Underlying mechanisms involve conditioning of antigen presenting cells (APC). Adoptively transferred CD8(+) T cells characterized by IL-16 secretion have also exhibited disease-inhibitory effects. In mice with polyarthritis, CD8(+) Ts suppressed inflammation by IFNgamma-mediated modulation of the tryptophan metabolism in APC. In SLE animal models, CD8(+) Ts induced by a synthetic peptide exerted suppressive activity mainly via the TGFbeta-Foxp3-PD1 pathway. CD8(+) Ts induced by histone peptides were found to downregulate disease activity by secreting TGFbeta. In essence, disease-specific approaches may be necessary to identify CD8(+) Ts optimally suited to treat immune dysfunctions in different autoimmune syndromes.
View details for DOI 10.1016/j.humimm.2008.08.283
View details for Web of Science ID 000261565500018
View details for PubMedID 18812196
T-cell co-stimulatory pathways in autoimmunity
ARTHRITIS RESEARCH & THERAPY
T-cell activation and differentiation depend on the signal strength received by the T-cell receptor and on signals provided by co-stimulatory molecules. The most prominent co-stimulatory molecule is CD28, which controls the activation of naïve and memory T cells by antigen presented on professional antigen-presenting cells. Blocking of the CD28-CD80/86 pathway has been an appealing strategy for inducing tolerance in autoimmune diseases where the disease-inducing autoantigens are not known. Although CD28 has maintained its unique position, the past decade has witnessed the recognition that a large number of regulatory molecules on T cells must be stimulated to generate a fully protective immune response. These regulatory receptors differ in their preferential expression on T-cell subsets, in the ligands that they recognize, and in the signaling pathways that they trigger. They have in common the fact that they provide information on the cellular environment in which the T-cell response occurs. By intercepting these signals, we may be able to influence disease-relevant T-cell responses in autoimmune diseases while potentially minimizing broad immunosuppression.
View details for DOI 10.1186/ar2414
View details for Web of Science ID 000264562800003
View details for PubMedID 19007423
T cells in arteritis and atherosclerosis
CURRENT OPINION IN LIPIDOLOGY
2008; 19 (5): 469-477
Inflammatory vasculopathies, spanning from atherosclerosis to vasculitides, are driven by innate and adaptive immune responses. Instructed by antigen-presenting cells, T cells have unsurpassed skills to orchestrate protective and pathogenic immunity. Pro-inflammatory and anti-inflammatory T cells regulate master pathogenic pathways, providing a framework for novel immunotherapeutic strategies.The multilayered wall of macrovessels creates a unique tissue niche; professional antigen-presenting cells, specifically dendritic cells, are superior in triggering and maintaining T-cell responses in this tissue milieu. Plaque-residing dendritic cells sense pathogen-derived motifs and edit inflammatory responses. T cells respond to antigen but antigen-nonspecific factors setting cellular response thresholds may be equally important. Dysregulated signal transduction pathways emerge as highly relevant in biasing T cells toward hyperresponsiveness. In the inflamed atheroma and in arteritic lesions, pathogenic T cells coordinate multiple injury pathways. Besides inducing tissue-damaging macrophage functions, they directly inflict cellular injury within the arterial wall. Distinctively, selected T cells induce smooth muscle cell apoptosis, most prominently by upregulating the death-receptor ligand TRAIL.Innate sentinels, specifically dendritic cells, populate normal arteries, intramural vasculitic lesions, and the inflamed atheroma. They sense microbial motifs and instruct T cells toward pro-inflammatory and tissue-destructive effector functions. Microenvironmental factors imposed by the unique structure of the arterial wall appear to be highly conserved across disease entities, modulating inflammation in atherosclerosis and arteritis.
View details for DOI 10.1097/MOL.0b013e32830bfdc2
View details for Web of Science ID 000259349800005
View details for PubMedID 18841594
Vessel-specific Toll-like receptor profiles in human medium and large arteries
2008; 118 (12): 1276-1284
Inflammatory vasculopathies, ranging from the vasculitides (Takayasu arteritis, giant cell arteritis, and polyarteritis nodosa) to atherosclerosis, display remarkable target tissue tropisms for selected vascular beds. Molecular mechanisms directing wall inflammation to restricted anatomic sites within the vascular tree are not understood. We have examined the ability of 6 different human macrovessels (aorta and subclavian, carotid, mesenteric, iliac, and temporal arteries) to initiate innate and adaptive immune responses by comparing pathogen-sensing and T-cell-stimulatory capacities.Gene expression analysis for pathogen-sensing Toll-like receptors (TLRs) 1 to 9 showed vessel-specific profiles, with TLR2 and TLR4 ubiquitously present, TLR7 and TLR9 infrequent, and TLR1, TLR3, TLR5, TLR6, and TLR8 expressed in selective patterns. Experiments with vessel walls stripped of the intimal or adventitial layer identified dendritic cells at the media-adventitia junction as the dominant pathogen sensors. In human artery-severe combined immunodeficiency (SCID) mouse chimeras, adoptively transferred human T cells initiated vessel wall inflammation if wall-embedded dendritic cells were conditioned with TLR ligands. Wall-infiltrating T cells displayed vessel-specific activation profiles with differential production of CD40L, lymphotoxin-alpha, and interferon-gamma. Vascular bed-specific TLR fingerprints were functionally relevant, as exemplified by differential responsiveness of iliac and subclavian vessels to TLR5 but not TLR4 ligands.Populated by indigenous dendritic cells, medium and large human arteries have immune-sensing and T-cell-stimulatory functions. Each vessel in the macrovascular tree exhibits a distinct TLR profile and supports selective T-cell responses, imposing vessel-specific risk for inflammatory vasculopathies.
View details for DOI 10.1161/CIRCULATIONAHA.108.789172
View details for Web of Science ID 000259224800009
View details for PubMedID 18765390
Epigenetic mechanisms of age-dependent KIR2DL4 expression in T cells
JOURNAL OF LEUKOCYTE BIOLOGY
2008; 84 (3): 824-834
Killer Ig-like receptor (KIR) expression is mostly restricted to NK cells controlling their activation. With increasing age, KIRs are expressed on T cells and contribute to age-related diseases. We examined epigenetic mechanisms that determine the competency of T cells to transcribe KIR2DL4. Compared with Jurkat cells and CD4(+)CD28(+) T cells from young individuals, DNA methyltransferase (DNMT) inhibition was strikingly more effective in T cells from elderly adults and the CD4(+)CD28(-) T cell line HUT78 to induce KIR2DL4 transcription. In these susceptible cells, the KIR2DL4 promoter was partially demethylated, and dimethylated H3-Lys 4 was increased, and all other histone modifications were characteristic for an inactive promoter. In comparison, NK cells had a fully demethylated KIR2DL4 promoter and the full spectrum of histone modifications indicative of active transcription with H3 and H4 acetylation, di- and trimethylated H3-Lys 4, and reduced, dimethylated H3-Lys 9. These results suggest that an increased competency of T cells to express KIR2DL4 with aging is conferred by a selective increase in H3-Lys 4 dimethylation and limited DNA demethylation. The partially accessible promoter is sensitive to DNMT inhibition, which is sufficient to induce full transcription without further histone acetylation and methylation.
View details for DOI 10.1189/jlb.0807583
View details for Web of Science ID 000258525500029
View details for PubMedID 18586981
The treatment of giant cell arteritis.
Reviews in neurological diseases
2008; 5 (3): 140-152
Although giant cell arteritis (GCA) is a well-known vasculitis sensitive to corticosteroid-mediated immunosuppression, numerous issues of long-term therapeutic management remain unresolved. Because GCA encompasses a broad spectrum of clinical subtypes, ranging from devastating visual loss and neurological deficits to isolated systemic symptoms, the treatment of GCA must be adjusted to each case, and recommendations vary widely in the literature. This article systematically reviews the treatment options for patients with neuro-ophthalmic and neurological complications of GCA, as well as the evidence for possible adjuvant therapies for patients with GCA. Although there is no randomized controlled clinical trial specifically evaluating GCA patients with ocular and neurological complications, we recommend that GCA patients with acute visual loss or brain ischemia be admitted to the hospital for high-dose intravenous methyl-prednisolone, close monitoring, and prevention of steroid-induced complications. Aspirin may also be helpful in these cases. The evidence supporting the use of steroid-sparing immunomodulatory agents such as methotrexate for long-term management remains debated.
View details for PubMedID 18838954
Defective proliferative capacity and accelerated telomeric loss of hematopoietic progenitor cells in rheumatoid arthritis
ARTHRITIS AND RHEUMATISM
2008; 58 (4): 990-1000
In rheumatoid arthritis (RA), telomeres of lymphoid and myeloid cells are age-inappropriately shortened, suggesting excessive turnover of hematopoietic precursor cells (HPCs). The purpose of this study was to examine the functional competence (proliferative capacity, maintenance of telomeric reserve) of CD34+ HPCs in RA.Frequencies of peripheral blood CD34+,CD45+ HPCs from 63 rheumatoid factor-positive RA patients and 48 controls matched for age, sex, and ethnicity were measured by flow cytometry. Proliferative burst, cell cycle dynamics, and induction of lineage-restricted receptors were tested in purified CD34+ HPCs after stimulation with early hematopoietins. Telomere sequences were quantified by real-time polymerase chain reaction. HPC functions were correlated with the duration, activity, and severity of RA as well as its treatment.In healthy donors, CD34+ HPCs accounted for 0.05% of nucleated cells; their numbers were strictly age dependent and declined at a rate of 1.3% per year. In RA patients, CD34+ HPC frequencies were age-independently reduced to 0.03%. Upon growth factor stimulation, control HPCs passed through 5 replication cycles over 4 days. In contrast, RA-derived HPCs completed only 3 generations. Telomeres of RA CD34+ HPCs were age-inappropriately shortened by 1,600 bp. All HPC defects were independent of disease duration, disease activity, and smoking status, and were present to the same degree in untreated patients.In RA, circulating bone marrow-derived progenitor cells were diminished, and concentrations stagnated at levels typical of those in old control subjects. HPCs from RA patients displayed growth factor nonresponsiveness and sluggish cell cycle progression; marked telomere shortening indicated proliferative stress-induced senescence. Defective HPC function independent of disease activity markers suggests bone marrow failure as a potential pathogenic factor in RA.
View details for DOI 10.1002/art.23287
View details for Web of Science ID 000255345200010
View details for PubMedID 18383391
TLR-mediated induction of negative regulatory ligands on dendritic cells
JOURNAL OF MOLECULAR MEDICINE-JMM
2008; 86 (4): 443-455
Dendritic cells (DCs) shape T-cell response patterns and determine early, intermediate, and late outcomes of immune recognition events. They either facilitate immunostimulation or induce tolerance, possibly determined by initial DC activation signals, such as binding Toll-like receptor (TLR) ligands. Here, we report that DC stimulation through the TLR3 ligand dsRNA [poly(I:C)] limits CD4 T-cell proliferation, curtailing adaptive immune responses. CD4+ T cells instructed by either lipopolysaccharide (LPS) or poly(I:C)-conditioned DCs promptly upregulated the activation marker CD69. Whereas LPS-pretreated DCs subsequently sustained T-cell clonal expansion, proliferation of CD4+ T cells exposed to poly(I:C)-pretreated DCs was markedly suppressed. This proliferative defect required DC-T cell contact, was independent of IFN-alpha, and was overcome by exogenous IL-2, indicating T-cell anergy. Coinciding with the downregulation, CD4+ T cells expressed the inhibitory receptor PD-1. Antibodies blocking the PD-1 ligand PD-L1 restored proliferation. dsRNA-stimulated DCs preferentially induced PD-L1, whereas poly(I:C) and LPS both upregulated the costimulatory molecule CD86 to a comparable extent. Poly(dA-dT), a ligand targeting the cytoplasmic RNA helicase pattern-recognition pathway, failed to selectively induce PD-L1 upregulation, assigning this effect to the TLR3 pathway. Poly(I:C)-conditioned DCs promoted accumulation of phosphorylated SHP-2, the intracellular phosphatase mediating PD-1 inhibitory effects. The ability of dsRNA to bias DC differentiation toward providing inhibitory signals to interacting CD4+ T cells may be instrumental in viral immune evasion. Conversely, TLR3 ligands may have therapeutic value in silencing pathogenic immune responses.
View details for DOI 10.1007/s00109-008-0310-x
View details for Web of Science ID 000255093600010
View details for PubMedID 18253710
T cell subset-specific susceptibility to aging
2008; 127 (1): 107-118
With increasing age, the competence of the immune system to fight infections and tumors declines. Age-dependent changes have been mostly described for human CD8 T cells, raising the question of whether the response patterns for CD4 T cells are different. Gene expression arrays of memory CD4 T cells yielded a similar age-induced fingerprint as has been described for CD8 T cells. In cross-sectional studies, the phenotypic changes were not qualitatively different for CD4 and CD8 T cells, but occurred much more frequently in CD8 T cells. Homeostatic stability partially explained this lesser age sensitivity of CD4 T cells. With aging, naïve and central memory CD8 T cells were lost at the expense of phenotypically distinct CD8 effector T cells, while effector CD4 T cells did not accumulate. However, phenotypic shifts on central memory T cells were also more pronounced in CD8 T cells. This distinct stability in cell surface marker expression can be reproduced in vitro. The data show that CD8 T cells are age sensitive by at least two partially independent mechanisms: fragile homeostatic control and gene expression instability in a large set of regulatory cell surface molecules.
View details for DOI 10.1016/j.clim.2007.12.002
View details for Web of Science ID 000254501700013
View details for PubMedID 18222733
Vessel wall-embedded dendritic cells induce T-Cell autoreactivity and initiate vascular inflammation
2008; 102 (5): 546-553
Human medium-sized and large arteries are targeted by inflammation with innate and adaptive immune responses occurring within the unique microspace of the vessel wall. How 3D spatial arrangements influence immune recognition and cellular response thresholds and which cell populations sense immunoactivating ligands and function as antigen-presenting cells are incompletely understood. To mimic the 3D context of human arteries, bioartificial arteries were engineered from collagen type I matrix, human vascular smooth muscle cells (VSMCs), and human endothelial cells and populated with cells implicated in antigen presentation and T-cell stimulation, including monocytes, macrophages, and myeloid dendritic cells (DCs). Responsiveness of wall-embedded antigen-presenting cells was probed with the Toll-like receptor ligand lipopolysaccharide, and inflammation was initiated by adding autologous CD4(+) T cells. DCs colonized the outermost VSMC layer, recapitulating their positioning at the media-adventitia border of normal arteries. Wall-embedded DCs responded to the microbial product lipopolysaccharide by entering the maturation program and upregulating the costimulatory ligand CD86. Activated DCs effectively stimulated autologous CD4 T cells, which produced the proinflammatory cytokine interferon-gamma and infiltrated deeply into the VSMC layer, causing matrix damage. Lipopolysaccharide-triggered macrophages were significantly less efficacious in recruiting T cells and promoting T-cell stimulation. CD14(+) monocytes, even when preactivated, failed to support initial steps of vascular wall inflammation. Innate immune cells, including monocytes, macrophages, and DCs, display differential functions in the vessel wall. DCs are superior in sensing pathogen-derived motifs and are highly efficient in breaking T-cell tolerance, guiding T cells toward proinflammatory and tissue-invasive behavior.
View details for DOI 10.1161/CIRCRESAHA.107.161653
View details for Web of Science ID 000253989500008
View details for PubMedID 18202318
Synoviocyte stimulation by the LFA-1-intercellular adhesion molecule-2-Ezrin-Akt pathway in rheumatoid arthritis
JOURNAL OF IMMUNOLOGY
2008; 180 (3): 1971-1978
In rheumatoid arthritis (RA), the synovium is infiltrated by mononuclear cells that influence the proliferation and activation of fibroblast-like synoviocytes (FLS) through soluble mediators as well as cell-to-cell contact. To identify receptor-ligand pairs involved in this cross-talk, we cocultured T cells with FLS lines isolated from synovial tissues from RA patients. Coculture with T cells induced phosphorylation of Akt (Ser(473)) and its downstream mediators, GSK-3alpha/GSK-beta, FoxO1/3a, and mouse double minute-2, and enhanced FLS proliferation. T cell-mediated phospho-Akt up-regulation was unique for FLS as no such effect was observed upon interaction of T cells with dendritic cells and B cells. Akt activation was induced by all functional T cell subsets independent of MHC/Ag recognition and was also found with other leukocyte populations, suggesting the involvement of a common leukocyte cell surface molecule. Akt phosphorylation, enhanced in vitro FLS proliferation, and enhanced FLS IL-6 production was inhibited by blocking Abs to CD11a and ICAM-2 whereas Abs to ICAM-1 had a lesser effect. Selective involvement of the LFA-1-ICAM-2 pathway was confirmed by the finding of increased ezrin phosphorylation at Tyr(353) that is known to be downstream of ICAM-2 and supports cell survival through Akt activation. CD28(-) T cells, which are overrepresented in RA patients, have high CD11a cell surface expression and induce Akt phosphorylation in FLS more potently than their CD28(+) counterparts. These findings identify ICAM-2 as a potential therapeutic target to inhibit FLS activation in RA, allowing for a more selective intervention than broad LFA-1 inhibition.
View details for Web of Science ID 000252632900075
View details for PubMedID 18209096
Synergistic proinflammatory effects of the antiviral cytokine interferon-alpha and toll-like receptor 4 ligands in the atherosclerotic plaque
2007; 116 (18): 2043-2052
Interferon (IFN)-alpha is a pluripotent inflammatory cytokine typically induced by viral infections. In rupture-prone atherosclerotic plaques, plasmacytoid dendritic cells produce IFN-alpha. In the present study we explored the contribution of IFN-alpha to inflammation and tissue injury in the plaque microenvironment.In 53% of carotid plaques (n=30), CD123+ plasmacytoid dendritic cells clustered together with CD11c+ myeloid dendritic cells, a distinct dendritic cell subset specialized in sensing danger signals from bacteria and tissue breakdown. Tissue concentrations of IFN-alpha and tumor necrosis factor (TNF)-alpha transcripts were tightly correlated (r=0.76, P<0.001), suggesting a regulatory role of IFN-alpha in TNF-alpha production. Plaque tissue stimulation with CpG ODN, a Toll-like receptor (TLR) 9 ligand, increased IFN-alpha production (57.8+/-23.7 versus 25.9+/-8.6 pg/mL; P<0.001), whereas the TLR4 ligand lipopolysaccharide induced TNF-alpha secretion (225.1+/-3.0 versus 0.7+/-0.2 pg/mL; P<0.001). Treating plaque tissue with IFN-alpha markedly enhanced lipopolysaccharide-triggered TNF-alpha secretion (559.0+/-25.9 versus 225.1+/-3.0 pg/mL; P<0.001). IFN-alpha pretreatment also amplified the effects of lipopolysaccharide on interleukin-12, interleukin-23, and matrix metalloproteinase-9, suggesting that the antiviral cytokine sensitized myeloid dendritic cells and macrophages toward TLR4 ligands. Mechanistic studies demonstrated that IFN-alpha modulated the myeloid dendritic cell response pattern by upregulating TLR4 expression (P<0.001) involving both the STAT (signal transducer and activator of transcription) and the PI(3)K pathway.In the atherosclerotic plaque, IFN-alpha functions as an inflammatory amplifier. It sensitizes antigen-presenting cells toward pathogen-derived TLR4 ligands by upregulating TLR4 expression and intensifies TNF-alpha, interleukin-12, and matrix metalloproteinase-9 production, all implicated in plaque destabilization. Thus, IFN-alpha-inducing pathogens, even when colonizing distant tissue sites, threaten the stability of inflamed atherosclerotic plaque.
View details for DOI 10.1161/CIRCULATIONAHA.107.697789
View details for Web of Science ID 000250518000008
View details for PubMedID 17938289
Fractalkine mediates T cell-dependent proliferation of synovial fibroblasts in rheumatoid arthritis
ARTHRITIS AND RHEUMATISM
2007; 56 (10): 3215-3225
In rheumatoid arthritis (RA), synovial fibroblasts proliferate excessively, eventually eroding bone and cartilage. The aim of this study was to examine the mechanisms through which CD4 T cells, the dominant lymphocyte population in patients with rheumatoid synovitis, regulate synoviocyte proliferation.Fibroblast-like synoviocyte (FLS) lines were established from rheumatoid synovium. CD4 T cells from patients with RA and age-matched control subjects were cultured on FLS monolayers. FLS proliferation was quantified by cytometry, using carboxyfluorescein succinimidyl ester staining or microscopic enumeration of PKH26-stained FLS. Surface expression of the fractalkine (FKN) receptor CX(3)CR1 was monitored by fluorescence-activated cell sorting. The induction of CX(3)CR1 and its ligand FKN in FLS was quantified by real-time polymerase chain reaction.The proliferation of FLS was significantly increased in the presence of CD4 T cells from patients with RA compared with control T cells. CD4+,CD28- T cells were particularly effective in supporting FLS growth, inducing a 25-fold expansion compared with a 5-fold expansion induced by CD4+,CD28+ T cells. The growth-promoting activity of CD4+,CD28- T cells was mediated through CX(3)CR1, a chemokine receptor expressed on both T cells and FLS. Anti-CX(3)CR1 antibodies inhibited T cell production of tumor necrosis factor alpha (TNFalpha) and suppressed FLS proliferation. TNFalpha amplified the expansion of FLS by enhancing their expression of CX(3)CR1 and FKN.FKN-CX(3)CR1 receptor-ligand interactions regulate FLS growth and FLS-dependent T cell function. FLS stimulate autocrine growth by releasing FKN and triggering the activity of their own CX(3)CR1. This growth-promotion loop is amplified by TNFalpha produced by CX(3)CR1-expressing T cells upon stimulation by FKN-expressing FLS. These data assign a critical role to FKN and its receptor in fibroblast proliferation and pannus formation in RA.
View details for DOI 10.1002/art.22919
View details for Web of Science ID 000250264800008
View details for PubMedID 17907166
Unchecked CD70 expression on T cells lowers threshold for T cell activation in rheumatoid arthritis
JOURNAL OF IMMUNOLOGY
2007; 179 (4): 2609-2615
Rheumatoid arthritis (RA) is characterized by premature immune aging with accumulation of degenerate T cells deficient for CD28. Gene expression profiling of CD4(+)CD28(-) and CD4(+)CD28(+) T cells to discover disease-promoting activities of CD28(-) T cells identified expression of CD70 as a most striking difference. Hence, CD70 was significantly more expressed in CD4 T cells from RA patients compared with age-matched controls (p < 0.006). The underlying mechanism was a failure to repress CD70 expression after activation-dependent induction. This defect in RA was not related to differential promoter demethylation. CD70 on bystander CD4(+)CD28(-) T cells functioned by lowering the threshold for T cell activation; admixture of CD4(+)CD28(-) T cells augmented TCR-induced responses of autologous naive CD4(+)CD28(+) T cells, particularly of low-avidity T cells. The data support a model in which CD70 expressed on T cells causes degeneracy in T cell responses and undermines tolerance mechanisms that normally control T cell autoreactivity.
View details for Web of Science ID 000248959200067
View details for PubMedID 17675524
Immunopathologic aspects of rheumatoid arthritis: Who is the conductor and who plays the immunologic instrument?
JOURNAL OF RHEUMATOLOGY
2007; 34: 9-14
The inflammatory process of rheumatoid arthritis (RA) resembles a symphony orchestra playing a piece of music--not a song that anyone wants to hear, but a song nevertheless. Each cellular player has a distinct role, and all must coordinate in order to play their discordant "music" successfully. Rheumatoid synovitis consists of resident cells and invading immune cells that together arrange the inflammatory process in RA. There are 3 major types of synovitis that RA can comprise: germinal center synovitis, aggregate synovitis, and diffuse synovitis. Germinal centers are highly organized complex structures that are functionally competent. Aggregates are B cells and T cells arranged in defined follicles, yet they lack germinal center reactions. Diffuse synovitis is the least organized but can still cause significant damage. For each of these types of synovitis, the cellular players and their molecular instruments vary significantly. Differences in lymphoid microorganizations draw attention to the process of lymphoid organogenesis as a fundamental pathway of rheumatoid synovitis, a process that lends stability and sustainability to dysfunctional immune responses. This article will address how tissue-resident and invading cells, in particular T cells, B cells, dendritic cells, and synoviocytes, are brought together in different "symphonic" arrangements and how this process of lymphoid organization affects disease outcome and therapeutic options in RA.
View details for Web of Science ID 000248275500003
The diagnosis of giant cell arteritis.
Reviews in neurological diseases
2007; 4 (3): 128-142
Giant cell arteritis (GCA) is the most common primary vasculitis in adults older than 50 years. The potential of GCA to cause bilateral, sequential vision loss makes it often a true neuro-ophthalmic emergency. Approximately one fifth of patients with GCA will present with ophthalmic complaints alone. The diagnosis of GCA requires a high index of suspicion and a systematic approach to diagnostic testing. The combination of abnormal laboratory markers of systemic inflammation and unilateral temporal artery biopsy is usually diagnostic. Additional testing with other diagnostic modalities may be required in cases in which clinical suspicion remains high despite a negative initial workup. We systematically review the diagnostic modalities used in suspected GCA patients who present with neuro-ophthalmic symptoms and signs.
View details for PubMedID 17943065
Aging and T-cell diversity
2007; 42 (5): 400-406
Naïve and memory CD4 and CD8 T cells constitute a highly dynamic system with constant homeostatic and antigen-driven proliferation, influx, and loss of T cells. Thymic activity dwindles with age and essentially ceases in the later decades of life, severely constraining the generation of new T cells. Homeostatic control mechanisms are very effective at maintaining a large and diverse subset of naïve CD4 T cells through the 7th decade of life, but eventually and abruptly fail at about the age of 75 years. In contrast, the CD8 T cell compartment is more unstable, with progressive diminution of naïve T cells and increasing loss of diversity during mid adulthood. Vaccination strategies need to aim at developing a broad repertoire of memory T cells before the critical time period when the naïve CD4 T-cell repertoire collapses. Research efforts need to aim at understanding T-cell homeostatic control mechanisms to ultimately expand the time period of repertoire stability.
View details for DOI 10.1016/j.exger.2006.11.016
View details for Web of Science ID 000246532900005
View details for PubMedID 17218073
Infliximab for maintenance of glucocorticosteroid-induced remission of giant cell arteritis - A randomized trial
ANNALS OF INTERNAL MEDICINE
2007; 146 (9): 621-630
Tumor necrosis factor-alpha is present in arteries in giant cell arteritis.To evaluate the efficacy of infliximab, an anti-tumor necrosis factor-alpha agent, in giant cell arteritis.Randomized, controlled trial.22 sites in the United States, the United Kingdom, Belgium, Italy, and Spain.44 patients with newly diagnosed giant cell arteritis that was in glucocorticosteroid-induced remission.Participants were randomly assigned in a 2:1 ratio to receive infliximab (5 mg/kg of body weight) or placebo. Sixteen patients were assigned to glucocorticosteroid plus placebo, and 28 patients to glucocorticosteroid plus infliximab.End points were measured through week 22, when an interim analysis resulted in early stopping of the planned 54-week trial. Primary end points were the number of patients who remained free of relapse through week 22 and adverse events. Secondary end points were time to first relapse, biomarkers, cumulative glucocorticosteroid dose, and the number of patients who remained relapse-free while the glucocorticosteroid dosage was tapered to 10 mg/d.Infliximab therapy did not increase the proportion of patients without relapse at week 22 compared with placebo (43% vs. 50%, respectively; difference, -7 percentage points [95% CI, -38 to 23 percentage points; P = 0.65), nor did it increase the proportion of patients whose glucocorticosteroid dosages were tapered to 10 mg/d without relapse (61% vs. 75%, respectively; difference, -14 percentage points [CI, -42 to 14 percentage points]; P = 0.31). The incidence of infection was 71% with infliximab and 56% with placebo (difference, 15 percentage points [CI, -14 to 45 percentage points]).The sample was too small to rule out modest effects of infliximab and included only patients with a new diagnosis. Only one dose of infliximab was evaluated, and the study was terminated early.This trial is too small to draw definitive conclusions, but it provides evidence that using infliximab as maintenance therapy in patients in glucocorticoid-induced remission of newly diagnosed giant cell arteritis is of no benefit and may be harmful. If infliximab has benefit, it is unlikely to be great. ClinicalTrials.gov registration number: NCT00076726.
View details for Web of Science ID 000246070500001
View details for PubMedID 17470830
Functional profile of activated dendritic cells in unstable atherosclerotic plaque
BASIC RESEARCH IN CARDIOLOGY
2007; 102 (2): 123-132
Unstable atherosclerotic plaque typically contains an infiltrate of activated macrophages and activated T cells. This study established a functional profile of plaque-residing dendritic cells (DC) to examine whether they can function as Ag-presenting cells to facilitate in situ T-cell activation.Carotid artery plaque tissues were collected from 19 asymptomatic and 38 symptomatic patients undergoing endarterectomy. Matched samples of normal coronary artery wall, stable nonruptured plaque, and eroded unstable plaque were harvested from patients with fatal myocardial infarction. Quantitative PCR and immunohistochemistry were used to analyze the tissues for markers of DC activation (CD83, CD86, CCL19,CCL21) and correlate them with T-cell activation (IFN-gamma,TNF-alpha).Carotid artery plaques from patients with ischemic symptoms compared to asymptomatic patients were characterized by the presence of high amount of T-cells (P<0.01) and tissue production of high levels of the T-cell cytokines IFN-gamma (P=0.001) and TNF-alpha (P=0.006). Plaque tissues from patients with ischemic complications contained elevated levels of CD83 (P<0.001), a marker of DC activation, and the DC chemokines CCL19 (P=0.001) and CCL21 (P<0.02). Unstable coronary artery plaques were similarly correlated compared to carotid plaques from symptomatic patients with the accumulation of T cells (P=0.001) and the production of T cell chemokines IFN-gamma (P=0.001) and TNF-alpha (P=0.002). Immunohistochemistry confirmed the presence of CD83(+) DC in the shoulder region of unstable plaques, where they produced the T cell-attracting chemokines CCL19 and CCL21. Mapping of activated DC demonstrated close contact between mature DC and T cells expressing the activation marker CD40 ligand (CD40L).Activated and fully mature DC are represented in the inflammatory infiltrate characteristic for unstable carotid and coronary atheroma. Such DC produce chemokines, and thus can regulate the cell traffic into the lesion. Through the expression of the costimulatory ligand CD86, plaque-residing DC can augment T-cell stimulation and provide optimal stimulation conditions for T lymphocytes, resembling the microenvironment in organized lymphoid tissues.
View details for DOI 10.1007/s00395-006-0636-x
View details for Web of Science ID 000243802600003
View details for PubMedID 17136419
Occurrence of giant cell arteritis...suddenly.
Transactions of the American Ophthalmological Society
2007; 105: 141-144
To define the kinetics and mechanisms of frank arteritis onset in patients with giant cell arteritis.Cytokines were analyzed from tissue of a patient before and after the development of arteritis.A temporal artery biopsy specimen from a patient with giant cell arteritis showed no pathologic changes on microscopic examination, but there was evidence of early tissue activation of inflammatory markers. A specimen from the contralateral artery 12 days later had high levels of IL-18 transcripts and abundant transcripts for CCL19. Also, CD83 and IL-1 were present, confirming that the vascular dendritic cells had fully matured. This second biopsy specimen showed floridly positive giant cell arteritis on histopathologic examination.Partial activation of vascular dendritic cells is typically seen in patients with polymyalgia rheumatica in whom no inflammatory infiltrates are seen on histomorphologic examination. Dendritic cells become activated at an early stage of arteritis, beginning the pathologically evident arteritis, and are fully matured in microscopically florid arteritis.
View details for PubMedID 18427603
Immune-mediated mechanisms in atherosclerosis: Prevention and treatment of clinical manifestations
CURRENT PHARMACEUTICAL DESIGN
2007; 13 (36): 3701-3710
Accumulation of inflammatory cells identifies atherosclerotic plaque at risk for rupture. Typically, activated immune cells occupy the rupture-prone areas of the atherosclerotic lesion. These cells are an appealing therapeutic target for novel strategies of plaque stabilization. Biologic consequences of plaque inflammation ultimately depend not only on the cellular players populating the lesion but also on triggers of immune activation originating from within the plaque or arriving from the circulation, and immune effector mechanisms that mediate cellular damage and plaque destabilization. Recent studies have provided insights into particular immune mechanisms in the atherosclerotic plaque that contribute to plaque vulnerability. This knowledge provides the basis for potential immunomodulatory therapies in cardiovascular disease. These therapeutic approaches can be classified as (1) immunomodulatory effects of existing therapies, (2) therapies targeting inflammatory triggers, and (3) agents inhibiting specific immune mechanisms.
View details for Web of Science ID 000253584200009
View details for PubMedID 18220809
Pathogen-sensing plasmacytoid dendritic cells stimulate cytotoxic T-cell function in the atherosclerotic plaque through interferon-alpha
2006; 114 (23): 2482-2489
Unstable atherosclerotic plaque is characterized by an infiltrate of inflammatory cells. Both macrophages and T cells have been implicated in mediating the tissue injury leading to plaque rupture; however, signals regulating their activation remain unidentified. Infectious episodes have been suspected to render plaques vulnerable to rupture. We therefore explored whether plasmacytoid dendritic cells (pDCs) that specialize in sensing bacterial and viral products can regulate effector functions of plaque-residing T cells and thus connect host infection and plaque instability.pDCs were identified in 53% of carotid atheromas (n=30) in which they localized to the shoulder region and produced the potent immunoregulatory cytokine interferon (INF)-alpha. IFN-alpha transcript concentrations in atheroma tissues correlated strongly with plaque instability (P<0.0001). Plaque-residing pDCs responded to pathogen-derived motifs, CpG-containing oligodeoxynucleotides binding to toll-like receptor 9, with enhanced IFN-alpha transcription (P=0.03) and secretion (P=0.007). IFN-alpha emerged as a potent regulator of T-cell function, even in the absence of antigen recognition. Specifically, IFN-alpha induced a 10-fold increase of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) on the surface of CD4 T cells (P<0.0001) and enabled them to effectively kill vascular smooth muscle cells (P=0.0003).pDCs in atherosclerotic plaque sense microbial motifs and amplify cytolytic T-cell functions, thus providing a link between host-infectious episodes and acute immune-mediated complications of atherosclerosis.
View details for DOI 10.1161/CIRCULATIONAHA.106.642801
View details for Web of Science ID 000243477500012
View details for PubMedID 17116765
Siravastatin suppresses endotoxin-induced upregulation of toll-like receptors 4 and 2 in vivo
2006; 189 (2): 408-413
In addition to lipid lowering effects, statins appear to have pleiotropic immunomodulatory properties. As they particularly affect monocyte functions, we tested the influence of statin treatment on the monocyte activating toll-like receptors (TLR) 4 and 2 in response to lipopolysaccharides (LPS) in vivo. In this double-blind, placebo-controlled study, 20 healthy, male subjects were randomized to receive either simvastatin (80 mg/day) or placebo for 4 days before intravenous LPS administration (20 IU/kg). Simvastatin did not influence the increase in TLR transcripts after LPS administration measured in mRNA isolated from whole blood by quantitative RT-PCR. In contrast, the parallel upregulation of TLR4 and TLR2 on the surface of monocytes determined by flow cytometry was attenuated by more than half after LPS challenge (P<0.02). Suppressed TLR4 and TLR2 expression was associated with diminished circulating concentrations of tumor necrosis factor-alpha and monocyte chemoattractant protein-1. In conclusion, high-dose simvastatin pretreatment blunted TLR4 and TLR2 expression on monocytes in a human endotoxemia model on a posttranscriptional level. This suppressive effect of statins on key receptors of the innate immunity which was associated with a reduction of effector cytokines reveals a potential mechanism for their beneficial effects in sepsis and cardiovascular disease.
View details for DOI 10.1016/j.atherosclerosis.2005.12.022
View details for Web of Science ID 000242305800022
View details for PubMedID 16443229
Treatment of chronic inflammatory diseases with biologic agents: Opportunities and risks for the elderly
2006; 41 (12): 1250-1255
The treatment armamentarium in rheumatic inflammatory diseases has drastically increased in the last years. Earlier uses of conventional disease-modifying antirheumatic drugs (DMARDs), along with the arrival of newer therapies including the so-called "biologic" agents, have provided better long-term outcomes for patients suffering from these illnesses. Biologic agents have shown efficacy for several diseases and failed in others. Due to a high prevalence of some of these diseases in the elderly population, this age group may also benefit, although treatment will have to be tailored to its special needs. In this mini review, we will discuss the use of these medications in rheumatic diseases with a significant prevalence in the elderly, their proven and potential uses, and the considerations that need to be taken into account when using them in this population.
View details for DOI 10.1016/j.exger.2006.10.010
View details for Web of Science ID 000243219800012
View details for PubMedID 17125948
- Immunosuppression in atherosclerosis mobilizing the opposition within CIRCULATION 2006; 114 (18): 1901-1904
Treatment of giant cell arteritis using induction therapy with high-dose glucocorticoids - A double-blind, placebo-controlled, randomized prospective clinical trial
ARTHRITIS AND RHEUMATISM
2006; 54 (10): 3310-3318
Glucocorticoid (GC) therapy for giant cell arteritis (GCA) is effective but requires prolonged administration, resulting in adverse side effects. The goal of the current study was to test the hypothesis that induction treatment with high-dose pulse intravenous (IV) methylprednisolone permits a shorter course of therapy.Twenty-seven patients with biopsy-proven GCA were enrolled in a randomized, double-blind, placebo-controlled study to receive IV methylprednisolone (15 mg/kg of ideal body weight/day) or IV saline for 3 consecutive days. All patients were started on 40 mg/day prednisone and followed the same tapering schedule as long as disease activity was controlled. The numbers of patients with disease in remission after 36, 52, and 78 weeks of treatment and taking
View details for DOI 10.1002/art.22163
View details for Web of Science ID 000241260800032
View details for PubMedID 17009270
Surgical pathology of noninfectious ascending aortitis: A study of 45 cases with emphasis on an isolated variant
AMERICAN JOURNAL OF SURGICAL PATHOLOGY
2006; 30 (9): 1150-1158
Aortitis is emerging as an important cause of ascending aortic aneurysm in the elderly. Its features have not been described in a surgical population.Retrospective clinicopathologic review of 45 cases of active noninfectious aortitis among 513 consecutive ascending aortic resections (1985 to 1999).Clinical data were collected from medical records. Histopathologic features were recorded during review of slides stained with hematoxylin-eosin and Verhoeff-van Gieson. Cases were categorized by predefined clinical criteria. Clinicopathologic features were compared among groups, with emphasis on unsuspected aortitis without systemic arteritis.The 2 largest groups were isolated aortitis (47%) and giant cell arteritis (31%). Other aortitis groups included Takayasu (14%), rheumatoid (4%), and unclassified (4%). Patients with isolated aortitis and giant cell arteritis were generally women (80%; mean age 73 y). All 6 with Takayasu arteritis were women (mean age 26). Although giant cell arteritis and isolated aortitis were histologically indistinguishable, their clinical courses differed substantially. Among 21 patients with isolated aortitis (2 treated with corticosteroids), only 10% later developed aortic aneurysms. In contrast, of 14 patients with giant cell arteritis (11 treated with corticosteroids), 21% subsequently developed aneurysms (P=0.09).Aortitis primarily affected women. Patients with isolated aortitis and giant cell arteritis were generally older than 50 years and, by definition, those with Takayasu arteritis were younger. In patients with isolated aortitis, outcomes were generally good, despite the absence of anti-inflammatory therapy. Accordingly, a conservative approach may be warranted for managing this subset of patients with aortitis.
View details for Web of Science ID 000240410000011
View details for PubMedID 16931960
Association of HLA-C3 and smoking with vasculitis in patients with rheumatoid arthritis
ARTHRITIS AND RHEUMATISM
2006; 54 (9): 2776-2783
To compare HLA-C genotypes and smoking habits in patients with vasculitis or other severe extraarticular manifestations of rheumatoid arthritis (ExRA) with those in RA patients without extraarticular disease.Patients were recruited from a large research database of patients with RA at the Mayo Clinic, from 2 Swedish cohorts of prevalent RA cases, and from a regional Swedish early RA cohort. Patients with severe ExRA (n = 159) and control patients with RA but no history of ExRA (non-ExRA controls) (n = 178) were matched for duration of RA and for clinical center. Data on smoking at RA onset, rheumatoid factor (RF) status, and antinuclear antibodies (ANAs) were extracted from the medical records. Polymerase chain reaction-based HLA-C genotyping was performed using a sequence-specific primer kit.The distribution of HLA-C alleles was significantly different between patients with RA-associated vasculitis and non-ExRA controls (P = 0.014). This was mainly due to a positive association of the HLA-C3 allele with vasculitis (allele frequency 0.411 in vasculitis patients versus 0.199 in non-ExRA controls; P < 0.001) and a decreased frequency of HLA-C7 (0.122 and 0.243, respectively; P = 0.018). The association between HLA-C3 and vasculitis was not due to linkage disequilibrium with HLA-DRB1. Smoking (P = 0.001), RF positivity (P < 0.0001), and presence of ANAs (P < 0.0001) were all associated with ExRA. HLA-C3 and smoking were both significant predictors of vasculitis in a multivariate model.Vasculitis in RA is associated with HLA-C3. Smoking is an independent predictor of vasculitis and other types of severe ExRA. Our results suggest that these variables are among the genetic and environmental factors that contribute significantly to the pathomechanisms of systemic RA.
View details for DOI 10.1002/art.22057
View details for Web of Science ID 000240872900008
View details for PubMedID 16947780
Uncoupling of T-cell effector functions by inhibitory killer immunoglobulin-like receptors
2006; 107 (11): 4449-4457
Killer immunoglobulin-like receptors (KIRs) are a family of regulatory cell-surface molecules expressed on natural killer (NK) cells and memory T-cell subsets. Their ability to prevent the formation of an activation platform and to inhibit NK cell activation is the basis of the missing self model of NK cell function. The benefits of KIR expression for T-cell biology are unclear. We studied how KIR2DL2 regulates T-cell function. Engagement of KIR2DL2 by the ligand human leukocyte antigen (HLA)-Cw3 did not affect conjugate formation between CD4(+)KIR2DL2(+) T cells and superantigen-pulsed target cells or the development of mature immune synapses with lipid rafts. KIR2DL2 and the corresponding HLA-C ligand were initially recruited to the peripheral supramolecular activation cluster (pSMAC). Consequently, KIR2DL2 engagement did not inhibit the phosphorylation of early signaling proteins and T-cell-receptor (TCR)-mediated cytotoxicity or granule exocytosis. After 15-30 minutes, KIR2DL2 moved to the central supramolecular activation cluster (cSMAC), colocalizing with CD3. TCR synapses dissociated, and phosphorylated phospholipase C (PLC)-gamma1, Vav1, and extracellular signal-regulated kinase 1/2 (ERK1/2) were reduced 90 minutes after stimulation. Gene array studies documented that the inhibition of late signaling events by KIR2DL2 affected transcriptional gene activation. We propose that KIRs on memory T cells operate to uncouple effector functions by modifying the transcriptional profile while leaving granule exocytosis unabated.
View details for Web of Science ID 000237877300041
View details for PubMedID 16469873
T cell recognition and killing of vascular smooth muscle cells in acute coronary syndrome
2006; 98 (9): 1168-1176
Loss of vascular smooth muscle cells (VSMCs) has been proposed to destabilize the atherosclerotic plaque and contribute to plaque rupture, superimposed thrombosis, and acute coronary syndromes (ACSs). We examined whether VSMCs are susceptible to T cell-induced apoptosis and found that CD4 T cells are highly effective in establishing cell-cell contact with VSMCs and triggering apoptotic death. Visualization of the T cell-VSMC contact zone on the single-cell level revealed that both patient-derived and control CD4 T cells reorganized their cell membrane to assemble an immunologic synapse with the VSMCs. Within 4 to 10 minutes, the membrane proximal signaling molecule ZAP-70 was recruited and phosphorylated. However, only patient-derived CD4 T cells sustained an intact immunologic synapse beyond 10 minutes and generated intracellular calcium signals. CD4 T cells that maintained a synaptic contact and appeared to be responsible for VSMC apoptosis accounted for approximately 20% of the circulating memory T cell population in ACS patients and were rare in the blood of age-matched controls. CD4 T cells from ACS patients were also hyperresponsive to T cell receptor-mediated stimulation when triggered by a superantigen and non-VSMC target cells. Lowered setting of the T cell activation threshold, attributable to excessive amplification of proximal CD3-mediated signals, may contribute to CD4 T cell-mediated killing of VSMCs and promote plaque instability.
View details for DOI 10.1161/01.RES.0000220649.10013.5c
View details for Web of Science ID 000237471600012
View details for PubMedID 16601227
Pathomechanisms in rheumatoid arthritis - time for a string theory?
JOURNAL OF CLINICAL INVESTIGATION
2006; 116 (4): 869-871
RA is a quintessential autoimmune disease with a growing number of cells, mediators, and pathways implicated in this tissue-injurious inflammation. Now Kuhn and colleagues have provided convincing evidence that autoantibodies reacting with citrullinated proteins, known for their sensitivity and specificity as biomarkers in RA, enhance tissue damage in collagen-induced arthritis (see the related article beginning on page 961). This study adds yet another soldier to the growing army of autoaggressive mechanisms that underlie RA. With great success researchers have dismantled the pathogenic subunits of RA, adding gene to gene, molecule to molecule, and pathway to pathway in an ever more complex scheme of dysfunction. The complexity of the emerging disease model leaves us speechless. It seems that with this wealth of data available, we need to develop a new theory for this disease. We may want to seek guidance from our colleagues in physics and mathematics who have successfully integrated their knowledge of elementary particles and the complexity of their interacting forces by formulating the string theory.
View details for DOI 10.1172/JCI28300
View details for Web of Science ID 000236556100008
View details for PubMedID 16585957
T-cell-targeted therapies in rheumatoid arthritis
NATURE CLINICAL PRACTICE RHEUMATOLOGY
2006; 2 (4): 201-210
T cells regulate the disease process in rheumatoid arthritis (RA) on multiple levels and represent a logical choice for anti-inflammatory therapy. In the inflamed joint they promote neoangiogenesis and lymphoid organogenesis, and stimulate synoviocyte proliferation and development of bone-eroding osteoclasts. The design of T-cell-targeted therapies for RA needs to take into account the uniqueness of T-cell generation, turnover and differentiation in affected patients. Patients accumulate 'old' T cells that respond to alternate regulatory signals because of an accelerated immune aging process; any therapeutic interventions that increase the replicative stress of T cells should, therefore, be avoided. Instead, therapeutic approaches that raise the threshold for T-cell activation are more promising. As a rule, antigen-derived signals synergize with co-stimulatory signals to stimulate T cells; such co-stimulatory signals are now targeted in novel immunosuppressive therapies. An example is abatacept (soluble cytotoxic-T-lymphocyte-associated protein 4-immunoglobulin), which binds with high affinity to CD80/CD86 and effectively suppresses inflammatory activity in RA. The therapeutic benefits gained by disrupting T-cell co-stimulation indicate that the pathogenesis of RA is driven by a more generalized abnormality in T-cell activation thresholds rather than a highly selective action of arthritogenic antigens.
View details for DOI 10.1038/ncprheum0142
View details for Web of Science ID 000236332300005
View details for PubMedID 16932686
Interleukin 12 induces T-cell recruitment into the atherosclerotic plaque
2006; 98 (4): 524-531
CD4 T cells, through the release of cytokines as well as direct effector functions, have been implicated in promoting inflammation of the atherosclerotic plaque. Plaque-infiltrating CD4 T cells include a specialized subset of (CD4+)CD28- T cells that express a unique profile of regulatory receptors and are responsive to novel microenvironmental cues. Here we report that (CD4+)CD28- T cells, either isolated from the plaque tissue or from the blood of patients with acute coronary syndrome (ACS), spontaneously express interleukin (IL)-12 receptors, even in the absence of antigenic stimulation. (CD4+)CD28- IL-12R+ cells responded to IL-12 stimulation with the upregulation of the chemokine receptor CCR5 and the C-type lectin receptor CD161, both implicated in regulating tissue homing of effector T cells. IL-12 treatment of (CD4+)CD28- T cells enhanced their chemotaxis and transendothelial migration toward the chemokine CCL5. In vivo relevance for the role of IL-12 in regulating the recruitment of (CD4+)CD28- T cells into the atheroma was examined in human atheroma-SCID mouse chimeras. Exposure of nonstimulated (CD4+)CD28- T cells to IL-12 was sufficient to amplify T-cell accumulation within the inflamed plaque, and coadministration of anti-CCR5 antibodies blocked T-cell recruitment into the plaque. Thus, (CD4+)CD28- T cells functionally resemble NK cells, which have proinflammatory activity even in the unprimed state and respond to any IL-12-inducing host infection with a shift in tissue trafficking and accrual in inflammatory lesions.
View details for DOI 10.1161/01.RES.0000204452.46568.57
View details for Web of Science ID 000235728300017
View details for PubMedID 16424368
Telomeres, immune aging and autoimmunity
2006; 41 (3): 246-251
Telomere length is important in constraining the replicative potential of cells; cellular systems that are dependent on cell replenishment for renewal or on cell proliferation for functionality are highly sensitive to telomeric erosion. Cell replication invariably leads to telomere loss, which, in some cellular systems, is partially compensated for by telomerase activity. In addition to this typical telomere loss, several mechanisms of sporadic telomere loss exist. Heterogeneity in age-dependent telomere loss can be a consequence of increased cellular turnover during a lifetime, accelerated telomeric DNA damage, or defects in telomere repair. The immune system is a prime example of a highly dynamic cellular system, for which telomere maintenance is pivotal. Immune competence is strictly dependent on rapid expansions of clonal T- and B-cell populations, and telomere loss may contribute to defective immune responses in the elderly. Equally interestingly, accelerated T-cell aging combined with telomeric shortening may predispose for autoimmune responses and thereby explain the increased susceptibility for chronic inflammatory diseases in the elderly.
View details for DOI 10.1016/j.exger.2005.12.002
View details for Web of Science ID 000236653300002
View details for PubMedID 16427234
- Lymphoma in rheumatoid arthritis: An immune system set up for failure ARTHRITIS AND RHEUMATISM 2006; 54 (3): 685-689
TRAIL-expressing T cells induce apoptosis of vascular smooth muscle cells in the atherosclerotic plaque
JOURNAL OF EXPERIMENTAL MEDICINE
2006; 203 (1): 239-250
Acute coronary syndromes (ACS) are precipitated by a rupture of the atherosclerotic plaque, often at the site of T cell and macrophage infiltration. Here, we show that plaque-infiltrating CD4 T cells effectively kill vascular smooth muscle cells (VSMC). VSMCs sensitive to T cell-mediated killing express the death receptor DR5 (TNF-related apoptosis-inducing ligand [TRAIL] receptor 2), and anti-TRAIL and anti-DR5 antibodies block T cell-mediated apoptosis. CD4 T cells that express TRAIL upon stimulation are expanded in patients with ACS and more effectively induce VSMC apoptosis. Adoptive transfer of plaque-derived CD4 T cells into immunodeficient mice that are engrafted with human atherosclerotic plaque results in apoptosis of VSMCs, which was prevented by coadministration of anti-TRAIL antibody. These data identify that the death pathway is triggered by TRAIL-producing CD4 T cells as a direct mechanism of VSMC apoptosis, a process which may lead to plaque destabilization.
View details for Web of Science ID 000235003600025
View details for PubMedID 16418392
Tissue trafficking patterns of effector memory CD4+T cells in rheumatoid arthritis
ARTHRITIS AND RHEUMATISM
2005; 52 (12): 3839-3849
Clonal populations of CD4+,CD28- T cells accumulating in rheumatoid arthritis functionally resemble end-differentiated, nondividing, short-lived effector memory cells that reside in peripheral tissues. We undertook this study to examine the tissue niche for CD4+,CD28- T cells and the signals regulating their survival and tissue homing patterns.Chemokine receptor expression on CD4+,CD28- T cell clones and peripheral blood lymphocytes was assessed by multicolor cytometry. In vitro chemotaxis and transendothelial migration were examined in a Transwell system. In vivo tissue-homing patterns were established by adoptively transferring fluorescence-labeled T cell clones into SCID mice engrafted either with rheumatoid synovium or with human lymph nodes.CD4+,CD28- T cell clones adoptively transferred into human tissue-SCID mouse chimeras infiltrated rheumatoid synovium but preferentially homed to lymph nodes. Such T cells coexpressed the chemokine receptors CCR7, CCR5, and CXCR4 and migrated in response to both inflammatory chemokines (CCL5) and homing chemokines (CXCL12). T cell receptor crosslinking abrogated chemotactic responsiveness. In contrast, interleukin-12 stimulation induced the up-regulation of CCR5 and a shift in the in vivo homing pattern away from the lymph nodes toward the inflamed synovium.CD4+,CD28- T cells resemble both short-lived effector memory cells and long-lived central memory cells, and they find a niche both in inflamed synovium and in lymph nodes. Nonspecific cytokine stimulation, not antigen recognition, triggers the transition from the lymph node to the synovium. By maintaining CCR7 expression, these end-differentiated T cells can home to lymphoid organs, enhance their survival, support clonal expansion, and perpetuate autoreactivity.
View details for DOI 10.1002/art.21482
View details for Web of Science ID 000234131500021
View details for PubMedID 16329093
Fractalkine receptor polymorphisms V249I and T280M as genetic risk factors for restenosis
THROMBOSIS AND HAEMOSTASIS
2005; 94 (6): 1251-1256
The chemokine fractalkine (FKN) recruits leukocytes into lesions of the arterial wall, which may lead to restenosis after stenting. FKN also regulates proliferation of smooth muscle cells, another mechanism pivotal to neointimal thickening. We assessed the hypothesis that functionally important polymorphisms of the FKN receptor CX3CR1 influence restenosis after coronary stenting. Three hundred and sixty-five patients undergoing coronary stenting were genotyped for the CX3CR1 polymorphisms V2491 and T280M. Restenosis occurred in 25% of patients, and recurrent (> 1) restenosis at the target lesion in 8%. The allele 1249 was associated with an increased risk of restenosis (adjusted odds ratio 2.4, 95% confidence interval: 1.3-4.2, P = 0.003) and recurrent restenosis (odds ratio 2.7, 95% confidence interval: 1.3-5.9, P = 0.011). Particularly, patients with 1249 lacking the allele M280 were at an elevated risk of restenosis (P = 0.006) and, accordingly, the haplotype containing 1249 but not M280 was more frequent in patients with restenosis (P = 0.001). In conclusion, the CX3CR1 1249 allele is associated with an increased risk of restenosis while the CX3CR1 M280 allele might counteract the harmful influence of 1249. These findings show the importance of the chemokine FKN and genetic variations of its receptor for restenosis after coronary stenting. Recognition of these inherited risk modifiers may help to individualize treatment of coronary stenosis.
View details for DOI 10.1160/TH05-06-0417
View details for Web of Science ID 000234214900023
View details for PubMedID 16411402
BLyS and APRIL in rheumatoid arthritis
JOURNAL OF CLINICAL INVESTIGATION
2005; 115 (11): 3083-3092
The cytokines B lymphocyte stimulator (BLyS) and a proliferation-inducing ligand (APRIL) enhance autoimmune disease by sustaining B cell activation. In RA, B cells contribute to the formation of 3 functionally distinct types of lymphoid microarchitectures in the inflamed synovium: ectopic GCs; T cell-B cell aggregates lacking GC reactions; and unorganized, diffuse infiltrates. We examined 72 tissues representing the 3 types of synovitis for BLyS and APRIL production and for expression of APRIL/BLyS receptors. Biologic effects of BLyS and APRIL were explored by treating human synovium-SCID mouse chimeras with the APRIL and BLyS decoy receptor transmembrane activator and CAML interactor:Fc (TACI:Fc). GC+ synovitis had the highest levels of APRIL, produced exclusively by CD83+ DCs. BLyS was present in similar levels in all tissue types and derived exclusively from CD68+ macrophages. In GC+ synovitis, treatment with TACI:Fc resulted in GC destruction and marked inhibition of IFN-gamma and Ig transcription. In contrast, inhibition of APRIL and BLyS in aggregate and diffuse synovitis left Ig levels unaffected and enhanced IFN-gamma production. These differential immunomodulatory effects correlated with the presence of TACI+ T cells in aggregate and diffuse synovitis and their absence in GC+ synovitis. We propose that BLyS and APRIL regulate B cell as well as T cell function and have pro- and antiinflammatory activities in RA.
View details for DOI 10.1172/JCI25265
View details for Web of Science ID 000233022100018
View details for PubMedID 16239971
T cell development and receptor diversity during aging
CURRENT OPINION IN IMMUNOLOGY
2005; 17 (5): 468-475
The T cell system is a complex and highly dynamic system that is amazingly robust over many decades of human life. Its functional competence is determined not only by its size but also by its diversity. Homeostatic control mechanisms have to secure sufficient T cell replenishment while preventing loss of clonal diversity. Major homeostatic challenges include profound expansion and shrinkage of T cell clonotypes upon antigenic triggering and, more importantly, age-related changes in T cell regeneration. The ability of the thymus to rebuild a diverse repertoire ceases in the fifth decade of life. Emerging data suggest that the end of the 7th decade of life defines a critical time period when T cell homeostasis is no longer guaranteed and diversity of the naïve T-cell repertoire collapses. Thus, failure of T cell homeostasis appears to result from cumulative defects of T cell generation. Elucidation of the underlying mechanisms will allow for extending this turning point to later in life; ultimately, interventions have to aim at restoring thymic function and complementary modes of T cell reconstitution.
View details for DOI 10.1016/j.coi.2005.07.020
View details for Web of Science ID 000231905800004
View details for PubMedID 16098723
Modulation of CD28 expression with anti-tumor necrosis factor alpha therapy in rheumatoid arthritis
ARTHRITIS AND RHEUMATISM
2005; 52 (10): 2996-3003
The immune system of patients with rheumatoid arthritis (RA) is characterized by the accumulation of CD4+ T cells deficient in CD28 expression and the up-regulation of tumor necrosis factor alpha (TNFalpha). Previous in vitro studies have shown that TNFalpha induces transcriptional silencing of the CD28 gene. Because reduced expression of CD28 in T cells compromises immunocompetence, we examined whether CD28 expression is reduced in patients with RA in vivo and whether the reduction is related to TNFalpha.Patients with RA and age-matched individuals were recruited. Peripheral blood mononuclear cells were stained for CD3, CD4, CD8, CD28, TNF receptor I (TNFRI), and TNFRII, and analyzed by quantitative flow cytometry. The number of CD28 and TNFR molecules was monitored in a subgroup of patients with RA undergoing treatment with anti-TNFalpha.In addition to higher frequencies of CD28null T cells, patients with RA had significantly reduced numbers of CD28 and TNFRI molecules on CD4+,CD28+ T cells. Normal expression could be restored in vitro by overnight culture, suggesting that CD28 in patients was modulated by exogenous factors. In contrast, treatment with TNFalpha in vitro resulted in further down-regulation. CD28 expression was normalized in patients undergoing TNFalpha-neutralizing therapy.Overproduction of TNFalpha in RA induces a global down-regulation of CD28 in CD4+ T cells and may cause reduced sensitivity to costimulatory signals in T cell responses.
View details for Web of Science ID 000232548800006
View details for PubMedID 16200579
Lipopolysaccharide, CD14 and Toll-like receptors: an emerging link between innate immunity and atherosclerotic disease.
2005; 1 (5): 657-674
Atherosclerosis and its clinical complications are now understood to be an inflammatory syndrome in which an ongoing systemic inflammatory response is combined with the accumulation of immune cells in the atherosclerotic plaque. Both arms of the immune system, innate and adaptive, have been implicated in contributing to essentially all stages of atherosclerosis, from initiation to progression and, ultimately, atherothrombotic complications. Innate immunity is the first line of defense against invading microorganisms. The recognition units of the innate immune system are designed to respond to molecular patterns shared by a variety of infectious microorganisms, such as bacterial lipopolysaccharide. Numerous basic and clinical studies have provided evidence that responsiveness to lipopolysaccharide may be correlated to the risk of atherosclerotic disease. The molecular basis of this connection appears to lie in Toll-like receptors that are expressed on cells of the innate immune system, bind to lipopolysaccharide, and thus determine the strength of antibacterial immune responses in the host. Variations in the function of Toll-like receptors and their signaling pathways are now suspected to play a critical role in determining the risk of atherosclerosis. This review summarizes recent research advances exploring the role of innate immunity, particularly lipopolysaccharide, CD14 and Toll-like receptors, in the initiation and development of atherosclerotic disease.
View details for DOI 10.2217/147966220.127.116.117
View details for PubMedID 19804106
Distinct transcriptional control mechanisms of killer immunoglobulin-like receptors in natural killer (NK) and in T cells
JOURNAL OF BIOLOGICAL CHEMISTRY
2005; 280 (25): 24277-24285
Killer immunoglobulin-like receptors (KIR) are expressed by natural killer (NK) cells and by subsets of CD4+ and CD8+ T cells, which are therefore thought to be subject to similar regulatory mechanisms. Here, we show that the transcriptional machinery to express KIR is limited to NK and T cells; however, the KIR transcriptional control differs between these two types of lymphocytes. T cells selectively express transcriptional activators binding to positions -52 to -61 of the KIR promoter, whereas an AML site around position-98 is relevant for transcription in NK cells. Although KIR expression is restricted to subsets of memory T cells, our studies demonstrate that transcriptional activators for KIRs are not acquired during T cell differentiation but are already present in naïve T cells, suggesting a basic role of KIRs in T cell biology. We suggest that the regulated expression of KIRs in T cells profoundly influences peripheral tolerance and antigen-specific immune responses.
View details for DOI 10.1074/jbc.M500727200
View details for Web of Science ID 000229880000105
View details for PubMedID 15863493
B cells as a therapeutic target in autoimmune diseases
EXPERT OPINION ON THERAPEUTIC TARGETS
2005; 9 (3): 431-445
Historically, the pathogenic role of B cells in autoimmune disease has been attributed to the formation of autoantibodies which, as soluble immunoglobulins or immunocomplexes, can trigger cellular damage and initiate the inflammatory cascade. Recent results from clinical trials applying B cell-directed therapeutics in rheumatoid arthritis and systemic lupus erythematosus have challenged such traditional views and encouraged novel ideas about the disease involvement of B cells. Suppression of disease activity, often disconnected from effects on autoantibody titers, has supported the notion that B cells may promote autoimmune disease by serving as antigen-presenting cells that sustain T cell activation. Likewise, B cells have been implicated in supporting the process of ectopic lymphoid neogenesis, a mechanism that stabilises pathogenic immune responses in target tissues and thus contributes to disease chronicity. As a general rule, clinical effects of B cell-directed therapeutics have often been unanticipated and unpredicted by experimental models, emphasis-ing the need to explore and verify disease principles in the patient.
View details for DOI 10.1517/1472818.104.22.1681
View details for Web of Science ID 000229916000002
View details for PubMedID 15948665
B cells in rheumatoid synovitis
ARTHRITIS RESEARCH & THERAPY
2005; 7: S9-S12
In rheumatoid arthritis, T cells, B cells, macrophages, and dendritic cells invade the synovial membranes, establishing complex microstructures that promote inflammatory/tissue destructive lesions. B cell involvement has been considered to be limited to autoantibody production. However, recent studies suggest that B cells support rheumatoid disease through other mechanisms. A critical element of rheumatoid synovitis is the process of ectopic lymphoid neogenesis, with highly efficient lymphoid architectures established in a nonlymphoid tissue site. Rheumatoid synovitis recapitulates the pathways of lymph node formation, and B cells play a key role in this process. Furthermore, studies of rheumatoid lesions implanted in immunodeficient mice suggest that T cell activation in synovitis is B cell dependent, indicating the role played by B cells in presenting antigens and providing survival signals.
View details for DOI 10.1186/ar1737
View details for Web of Science ID 000231215500003
View details for PubMedID 15960820
The influence of age on T cell generation and TCR diversity
JOURNAL OF IMMUNOLOGY
2005; 174 (11): 7446-7452
The ability to mount protective immune responses depends on the diversity of T cells. T cell diversity may be compromised by the declining thymic output of new T cells. The aging process imposes a threat to diversity, because thymic function deteriorates. In this study we have examined the relationship between thymic production, homeostatic T cell proliferation and TCR beta-chain diversity in young (approximately 25 years), middle-aged ( approximately 60 years), and elderly adults (approximately 75 years). TCR excision circles (TREC) as a marker of thymic output exponentially decreased by >95% between 25 and 60 years of age. The frequency of Ki67(+) cycling CD4 T cells remained steady, and surprisingly, the diversity of the naive CD4 T cell repertoire was maintained at approximately 2 x 10(7) different TCR beta-chains. After the age of 70 years, TRECs only slightly declined, but homeostatic proliferation doubled. The diversity of the T cell pool drastically contracted to 200,000 TCR beta-chains. Also, the phenotypic distinction between naive and memory CD4 T cells became fuzzy. The collapse in CD4 T cell diversity during the seventh and eighth decades indicates substantial T cell loss and implies that therapeutic measures to improve vaccine responses will have to include strategies for T cell replenishment.
View details for Web of Science ID 000229298400109
View details for PubMedID 15905594
Cell-based immunotherapy with suppressor CD8(+) T cells in rheumatoid arthritis
JOURNAL OF IMMUNOLOGY
2005; 174 (11): 7292-7301
The chronic persistence of rheumatoid synovitis, an inflammation driven by activated T cells, macrophages, and fibroblasts causing irreversible joint damage, suggests a failure in physiologic mechanisms that down-regulate and terminate chronic immune responses. In vitro CD8(+)CD28(-)CD56(+) T cells tolerize APCs, prevent the priming of naive CD4(+) T cells, and suppress memory CD4(+) T cell responses. Therefore, we generated CD8(+)CD28(-)CD56(+) T cell clones from synovial tissues, expanded them in vitro, and adoptively transferred them into NOD-SCID mice engrafted with synovial tissues from patients with rheumatoid arthritis. Adoptively transferred CD8(+)CD28(-)CD56(+) T cells displayed strong anti-inflammatory activity. They inhibited production of IFN-gamma, TNF-alpha, and chemokines in autologous and HLA class I-matched heterologous synovitis. Down-regulation of costimulatory ligands CD80 and CD86 on synovial fibroblasts was identified as one mechanism of immunosuppression. We propose that rheumatoid synovitis can be suppressed by cell-based immunotherapy with immunoregulatory CD8(+) T cells.
View details for Web of Science ID 000229298400091
View details for PubMedID 15905576
Opposite effects of CX3CRI receptor polymorphisms V2491 and T280M on the development of acute coronary syndrome - A possible implication of fractalkine in inflammatory activation
THROMBOSIS AND HAEMOSTASIS
2005; 93 (5): 949-954
Several lines of evidence suggest that the chemokine fractalkine (FKN) and its receptor CX3CR1 contribute to the accumulation of leukocytes in the atherosclerotic plaque. The M280 allele of the CX3CR1T280M polymorphism modulates leukocyte recruitment and is associated with lower prevalence of cardiovascular disease. The influence of V249I, another CX3CR1 polymorphism, is discussed controversially. We investigated the association of the alleles M280 and I249 of CX3CR1 with coronary artery disease (CAD) and with acute coronary syndrome (ACS). Additionally, we assessed their association with the soluble ligand FKN and inflammatory activation measured by high sensitivity C-reactive protein (hsCRP). The genotypes of the V249I and T280M polymorphisms were determined in 1152 patients with suspected CAD.720 (62.5%) individuals showed significant CAD with an ACS prevalence of 59.3%. Using multivariate regression, we found a harmful influence of I249 (adjusted OR=1.8, P<0.03) and a protective effect of M280 (adjusted OR=0.6, P<0.04) on the occurrence of ACS in patients with CAD. Correspondingly, patients with I249 but without M280 (17%) were at elevated risk of ACS (OR=1.6, P<0.04). During ACS these patients (carrying only I249) had significantly higher circulating concentrations of FKN and high sensitivity C-reactive protein (1.9- and 1.6-fold). We found no association of the I249 or the M280 allele with the occurrence of CAD. In conclusion, I249 and M280 have opposite effects on the occurrence of ACS. The presence of I249 not "balanced" by M280 confers an elevated risk of ACS. A FKN-mediated enhanced inflammatory activation might explain this increased risk.
View details for DOI 10.1160/TH04-11-0735
View details for Web of Science ID 000229087200025
View details for PubMedID 15886814
T cell costimulation by fractalkine-expressing synoviocytes in rheumatoid arthritis
ARTHRITIS AND RHEUMATISM
2005; 52 (5): 1392-1401
Patients with rheumatoid arthritis (RA) accumulate prematurely aged T cells that have acquired a new profile of regulatory receptors. Many of the de novo-expressed receptors are typically found on natural killer cells, including CX(3)CR1, the receptor for the chemokine fractalkine (FKN). This study explored whether interactions between CX(3)CR1 and FKN are relevant for T cell functions in rheumatoid synovitis.FKN expression was examined by real-time polymerase chain reaction and immunohistochemistry. CX(3)CR1 expression on peripheral blood T cells was analyzed by flow cytometry. T cell activation was quantified by determining proliferative responses, interferon-gamma (IFNgamma) secretion, and granule release. Fibroblast-like synoviocyte (FLS)/T cell adhesion was measured by the retention of 5-carboxyfluorescein diacetate succinimidyl ester-labeled T cells on FLS monolayers.FKN was expressed on cultured synovial fibroblasts and hyperplastic synoviocytes in the rheumatoid tissue. Among CD4+ T cells, only senescent CD28- T cells were positive for CX(3)CR1 (P < 0.001). Such CD4+,CD28-,CX(3)CR1+ T cells strongly adhered to FLS, with soluble FKN blocking the interaction. FKN expressed on FLS costimulated T cell-activating signals and amplified proliferation, IFNgamma production, and expulsion of cytoplasmic granules.Senescent CD4+ T cells that accumulate in rheumatoid arthritis aberrantly express CX(3)CR1. FKN, which is membrane-anchored on synoviocytes, enhances CD4+ T cell adhesion, provides survival signals, and costimulates the production of proinflammatory cytokines as well as the release of granules. By virtue of their altered receptor profile, senescent CD4+ T cells receive strong stimulatory signals from nonprofessional antigen-presenting cells in the synovial microenvironment.
View details for DOI 10.1002/art.21140
View details for Web of Science ID 000229004600007
View details for PubMedID 15880821
Toll-like receptors in giant cell arteritis
2005; 115 (1): 38-46
Giant cell arteritis, a primary vasculitis of medium-sized and large arteries, causes vessel occlusion through fast and concentric intimal hyperplasia. Contextual parameters, especially the topography of the arterial wall, have emerged as critical pathogenic elements. Experimental data support the concept that the disease is initiated in the most outer layer of the arterial wall, the adventitia. CD4 T cells are recruited to the adventitia, undergo local activation and subsequently orchestrate macrophage differentiation. T cells and macrophages infiltrate into all wall layers and acquire different effector functions dependent on cues in their immediate microenvironment. The end result is myofibroblastic proliferation, luminal stenosis, and tissue ischemia. Adaptive immune responses in the adventitia are triggered by a population of indigenous dendritic cells (DC) placed at the adventitia-media junction. These arterial DCs have a unique surface receptor profile, including a series of Toll-like receptors (TLR). Responsiveness of such arterial DCs to blood-borne stimuli has been studied in human arteries engrafted into immunodeficient mice. Ligands of TLR4 are able to start maturation of adventitial DCs which fail to leave the peripheral tissue site. Instead, these adventitial DCs produce chemokines, recruit T cells, and support their local activation. These data identify tissue-residing DCs as gatekeepers in vasculitis and support the model that TLR ligands function as instigators of vessel wall inflammation.
View details for DOI 10.1016/j.clin.2005.02.009
View details for Web of Science ID 000229096800007
View details for PubMedID 15870019
2005; 204: 55-73
Therapeutic efficacy of depleting B cells or blocking T-cell costimulation in rheumatoid arthritis (RA) has confirmed the critical pathogenic role of adaptive immune responses. Yet, RA preferentially affects elderly individuals, in whom adaptive immunity to exogenous antigens begins to fail. Here, we propose that senescence of the immune system is a risk factor for RA, with chronic inflammation resulting from the accumulation of degenerate T cells that have a low threshold for activation and utilize a spectrum of novel receptors to respond to microenvironmental cues. The process of immunosenescence is accelerated in RA and precedes the onset of disease, the acceleration, in part, being conferred by the HLA-DR4 haplotype. Naive CD4(+) T cells in RA are contracted in diversity and restricted in clonal burst. Senescence of effector CD4(+) T cells is associated with the loss of CD28 and the de novo expression of KIR2DS2, NKG2D, and CX(3)CR1, all of which function as costimulatory molecules and reduce the threshold for T-cell activation. The synovial microenvironment promotes chronic persistent immune responses by facilitating ectopic lymphoid neogenesis, such as the formation of aberrant germinal centers. With the propensity to develop complex lymphoid architectures and to provide optimal activation conditions for senescent CD4(+) T cells, the synovium becomes a natural target for pathogenic immune responses in prematurely aged individuals.
View details for Web of Science ID 000227672500005
View details for PubMedID 15790350
Vascular dendritic cells in giant cell arteritis
HUMAN IMMUNOLOGY: PATIENT-BASED RESEARCH
2005; 1062: 195-208
Giant cell arteritis (GCA) is a granulomatous vasculitis that selectively targets medium-sized and large arteries, especially the cranial branches of the aorta. The inflammatory activity of vascular lesions is driven by adaptive immune responses, with CD4 T cells undergoing clonal expansion in the vessel wall and releasing interferon gamma. Recent studies have described a distinctive population of dendritic cells (DCs) localized at the adventitia-media border of normal medium-sized arteries that appear to play a critical role in the initiation of vasculitis. Immune effector functions of this DC population are being examined in human artery-severe combined immunodeficient (SCID) mouse chimeras. In their constitutive form, CD11c+ fascin+ adventitial DCs are not recognized by alloreactive T cells. Triggering with Toll-like receptor (TLR) ligands is sufficient to break this state of tolerance and initiate DC activation, T-cell recruitment, T-cell activation, and T-cell retention in the arterial wall. Systemic administration of ligands for TLR2 or -4 in human artery-SCID chimeras drives differentiation of adventitial DCs into chemokine-producing effector cells with high-level expression of both CD83 and CD86 and mediates T-cell regulatory function through release of interleukin 18. In established vasculitis, fully matured DCs retain antigen-presenting function; antibody-mediated DC depletion disrupts T-cell and macrophage activation and has marked anti-inflammatory effects. We conclude that adventitial DCs, an indigenous cell population of the arterial wall, are responsive to pathogen-derived macromolecules and have gatekeeper function in regulating T-cell recruitment and retention to the arterial adventitia. A switch of adventitial DCs from being nonstimulatory to T-cell activating emerges as a critical event in the initiation of vasculitis.
View details for DOI 10.1196/annals.1358.023
View details for Web of Science ID 000236473100020
View details for PubMedID 16461802
Costimulatory pathways in rheumatoid synovitis and T-cell senescence
HUMAN IMMUNOLOGY: PATIENT-BASED RESEARCH
2005; 1062: 182-194
The pathogenesis of rheumatoid arthritis (RA) is determined by a complex interaction of genetic and environmental factors. Of all risk factors, age has the largest impact. RA occurs most often during the postmenopausal period of life, with incidence rates peaking in the eighth decade. While age is generally accepted as an etiologic factor for failure of immunocompetence, much less is understood about the role of T-cell senescence in autoimmunity. We have hypothesized that senescent T cells are particularly prone to be activated in specialized microenvironments, such as the synovial membrane. CD4 T cells in the senescence program were identified by the loss of CD28. Gene expression profiling documented that CD28- T cells have acquired a spectrum of regulatory receptors that are usually seen only on NK cells. Such regulatory receptors include stimulatory and inhibitory members of the killer immunoglobulin-like receptor (KIR) family, the stimulatory c-type lectin receptor NKG2D, and CX3CR1, the receptor for the chemokine fractalkine. Synovial fibroblasts express the relevant ligands, thus providing stimulatory signals to tissue-infiltrating T cells. The signaling pathways of these regulatory receptors are complex and dependent on the individual T cells, some of which express important adapter molecules such as DAP10 and DAP12. Inhibitory KIRs on T cells are often only partially functional. Our data suggest that, by virtue of altered receptor profiles, conventional tolerance mechanisms can be evaded in the aging host. By acquiring a new set of regulatory receptors, senescent CD4 T cells become responsive to novel environmental cues and find ideal stimulatory conditions in the synovial microenvironment.
View details for DOI 10.1196/annals.1358.022
View details for Web of Science ID 000236473100019
View details for PubMedID 16461801
Increased CD4+ T cell infiltrates in rheumatoid arthritis-associated interstitial pneumonitis compared with idiopathic interstitial pneumonitis
ARTHRITIS AND RHEUMATISM
2005; 52 (1): 73-79
To study lymphocyte markers in rheumatoid arthritis (RA)-associated interstitial pneumonitis (IP) compared with idiopathic IP.Paraffin-embedded lung biopsy specimens from patients with RA (n = 15) and from those without RA (n = 16), all of whom had a diagnosis of either nonspecific IP or usual IP, were studied. Tissue sections from each patient were reviewed by a pathologist, who was blinded to the clinical data. Age and pulmonary function test results were similar in RA and non-RA patients. After high-temperature antigen unmasking, sections were incubated with mouse monoclonal antibodies directed against CD3, CD4, CD8, CD16, and CD20. All slides were coded, and digital images (100x magnification) of the entire tissue area were obtained. Staining was quantified using computer-assisted image analysis.Staining for CD4 was more prominent in patients with RA than in the non-RA comparison group (median 9.3 cells/mm(2), interquartile range [IQR] 5.5-27.3 versus 0.6 cells/mm(2), IQR 0.2-1.9; P = 0.002). CD4+ cell counts were increased in RA patients with nonspecific IP as well as in RA patients with usual IP, with no major difference between these groups. Results were similar for quantification of CD3 (P = 0.012). There was a less striking trend toward more CD8+ cells in RA patients (P = 0.27 versus those with non-RA lung disease).IP lesions in patients with RA are characterized by an increased number of CD4+ cells, as compared with that in patients with idiopathic IP. This finding suggests that CD4+ T cells are critical for the development of pulmonary manifestations in RA, and may have implications for the treatment of RA-associated lung disease.
View details for DOI 10.1002/art.20765
View details for Web of Science ID 000226507700010
View details for PubMedID 15641082
The impact of HLA-DRB1 genes on extra-articular disease manifestations in rheumatoid arthritis
ARTHRITIS RESEARCH & THERAPY
2005; 7 (6): R1386-R1393
The objective of this study was to examine HLA-DRB1 and HLA-DQB1 genotypes in patients with severe extra-articular rheumatoid arthritis (ExRA) and to compare them with the genotypes of rheumatoid arthritis (RA) patients without extra-articular manifestations. Patients with severe ExRA were recruited from a large research database of patients with RA, from two cohorts of prevalent RA cases, and from a regional multicenter early RA cohort. Cases with ExRA manifestations (n = 159) were classified according to predefined criteria. Controls (n = 178) with RA but no ExRA were selected from the same sources. Cases and controls were matched for duration of RA and for clinical center. PCR based HLA-DRB1 and HLA-DQB1 genotyping was performed using the Biotest SSP kit, with additional sequencing in order to distinguish DRB1*04 subtypes. Associations between alleles and disease phenotypes were tested using multiple simulations of random distributions of alleles. There was no difference in global distribution of HLA-DRB1 and HLA-DQB1 alleles between patients with ExRA and controls. DRB1*0401 (P = 0.003) and 0401/0401 homozygosity (P = 0.002) were more frequent in Felty's syndrome than in controls. The presence of two HLA-DRB1*04 alleles encoding the shared epitope (SE) was associated with ExRA (overall odds ratio 1.79, 95% confidence interval 1.04-3.08) and with rheumatoid vasculitis (odds ratio 2.44, 95% confidence interval 1.22-4.89). In this large sample of patients with ExRA, Felty's syndrome was the only manifestation that was clearly associated with HLA-DRB1*0401. Other ExRA manifestations were not associated with individual alleles but with DRB1*04 SE double dose genotypes. This confirms that SE genes contribute to RA disease severity and ExRA. Other genetic and environmental factors may have a more specific impact on individual ExRA manifestations.
View details for DOI 10.1186/ar1837
View details for Web of Science ID 000234272000032
View details for PubMedID 16277691
Rheumatoid arthritis is an independent risk factor for multi-vessel coronary artery disease: a case control study
ARTHRITIS RESEARCH & THERAPY
2005; 7 (5): R984-R991
The risk for cardiovascular (CV) disease is increased in rheumatoid arthritis (RA) but data on the burden of coronary atherosclerosis in patients with RA are lacking. We conducted a retrospective case-control study of Olmsted County (MN, USA) residents with RA and new-onset coronary artery disease (CAD) (n = 75) in comparison with age-and sex-matched controls with newly diagnosed CAD (n = 128). Angiographic scores of the first coronary angiogram and data on CV risk factors and CV events on follow-up were obtained by chart abstraction. Patients with RA were more likely to have multi-vessel coronary involvement at first coronary angiogram compared with controls (P = 0.002). Risk factors for CAD including diabetes, hypertension, hyperlipidemia, and smoking history were not significantly different in the two cohorts. RA remained a significant risk factor for multi-vessel disease after adjustment for age, sex and history of hyperlipidemia. The overall rate of CV events was similar in RA patients and controls; however, there was a trend for increased CV death in patients with RA. In a nested cohort of patients with RA and CAD (n = 27), we measured levels of pro-inflammatory CD4+CD28null T cells by flow cytometry. These T cells have been previously implicated in the pathogenesis of CAD and RA. Indeed, CD4+CD28null T cells were significantly higher in patients with CAD and co-existent RA than in controls with stable angina (P = 0.001) and reached levels found in patients with acute coronary syndromes. Patients with RA are at increased risk for multi-vessel CAD, although the risk of CV events was not increased in our study population. Expansion of CD4+CD28null T cells in these patients may contribute to the progression of atherosclerosis.
View details for DOI 10.1186/ar1775
View details for Web of Science ID 000231020200008
View details for PubMedID 16207339
Thrombospondin 2 functions as an endogenous regulator of angiogenesis and inflammation in rheumatoid arthritis
AMERICAN JOURNAL OF PATHOLOGY
2004; 165 (6): 2087-2098
Thrombospondin 2 (TSP2), a matricellular protein with a primary role in modulating cell-matrix interactions, has been implicated in tissue repair and foreign body responses. Here we show that TSP2 has regulatory function in the chronic inflammatory lesions of rheumatoid arthritis. Tissue TSP2, produced by synovial fibroblasts, endothelial cells, and macrophages correlated not only with the intensity of angiogenesis but also with the architecture of lymphoid infiltrates. Synovial tissues with diffuse inflammatory infiltrates had high levels of TSP2, whereas synovial tissues with ectopic germinal center reactions and T cell-B cell aggregates produced low levels. Cell-based gene therapy with TSP2 was used to examine the in vivo effects of the matrix protein on neoangiogenesis and lymphoid organization. Human synovium-severe combined immunodeficiency (SCID) mouse chimeras were treated with TSP2-transfected fibroblasts deposited into the peritoneum. Overexpression of TSP2 led to the accumulation of TSP2 protein in the inflamed synovium and resulted in a prompt inhibition of lesional vascularization. Beside its anti-angiogenic activity, TSP2 also suppressed the production of the proinflammatory mediators, interferon-gamma and tumor necrosis factor-alpha, and induced the depletion of tissue-residing T cells. We propose that TSP2 is an endogenous regulator of angiogenesis and autoimmune inflammation in the synovium and represents a protective mechanism preventing ectopic lympho-organogenesis and persistent inflammation in this tissue site.
View details for Web of Science ID 000225381100023
View details for PubMedID 15579451
- Genetics of rheumatoid arthritis: Is there a pattern predicting extraarticular manifestations? ARTHRITIS & RHEUMATISM-ARTHRITIS CARE & RESEARCH 2004; 51 (5): 853-863
Stimulatory killer Ig-like receptors modulate T cell activation through DAP12-dependent and DAP12-independent mechanisms
JOURNAL OF IMMUNOLOGY
2004; 173 (6): 3725-3731
Stimulatory killer Ig-like receptors (KIRs) are expressed by various lymphocytes, including NK cells and subsets of T cells. In NK cells, KIRs associate with the adapter molecule KARAP/DAP12, which confers the ability to function as an independent activation unit. The function of KIRs and killer cell activating receptor-associated protein (KARAP)/DAP12 in T cells is unclear. By flow cytometry, we demonstrated that CD4+CD28null T cells heterogeneously express KIRs and/or KARAP/DAP12. In clones that lacked expression of KARAP/DAP12, the stimulatory KIR KIR2DS2 signaled through the JNK pathway, but did not activate the ERK pathway. However, in the presence of KARAP/DAP12, stimulation through KIR2DS2 led to phosphorylation of both JNK and ERK. Transfection experiments confirmed that KIR2DS2-mediated ERK phosphorylation was dependent on KARAP/DAP12. The differential signaling of KIR2DS2 through association with alternative adapter molecules resulted in differential regulation of cellular activity. In clones that lacked expression of KARAP/DAP12, stimulation of KIR2DS2 did not induce cytotoxicity. However, KIR2DS2 did augment suboptimal TCR stimulation, leading to enhanced IFN-gamma production. In clones that expressed KARAP/DAP12, KIR2DS2 directly activated both cytotoxicity and IFN-gamma production without the need for TCR-derived signals. The function of stimulatory KIRs in T cells is determined by the expression of the appropriate adapter molecule. Expression of KARAP/DAP12 is sufficient to convert a costimulatory KIR into a stimulatory molecule. These differing functions mediated by alternative signaling pathways have implications for the pathogenesis of diseases such as rheumatoid arthritis and acute coronary syndromes, in which aberrant expression of KIRs on T cells is frequently observed.
View details for Web of Science ID 000223878000019
View details for PubMedID 15356118
VEGF gene polymorphisms and susceptibility to rheumatoid arthritis
2004; 43 (9): 1173-1177
To investigate polymorphisms of the VEGF gene in patients with rheumatoid arthritis (RA), their relationship to clinical features and the radiographic progression of joint disease.One hundred and forty patients with RA and 149 healthy unrelated controls were recruited. We examined four polymorphisms of the VEGF gene which are reported to be associated with production of vascular endothelial growth factor (VEGF), using polymerase chain reaction (PCR) restriction fragment length polymorphism assay and amplification refractory mutation system (ARMS) PCR. Haplotypes were predicted by Bayesian algorithm using the Phase program.All four polymorphisms were in Hardy-Weinberg equilibrium in both patients and controls. The frequency of the 936 T allele, which has been associated with lower production of VEGF, was significantly increased in RA patients compared with controls (22.7 vs 13.4%, P = 0.002). The frequencies of two haplotypes (CGCT and AAGT) which were predicted using the Phase program were significantly increased in RA patients compared with controls [33 vs 14%, odds ratio (OR) 2.636, 95% confidence interval (CI) 1.38-5.04 for CGCT; 17 vs 6%, OR 3.08, 95% CI 1.20-7.92 for AAGT]. The carriers of the susceptible haplotypes in RA patients had a younger age at disease onset but did not show a difference in the progression rate of radiographic joint destruction.Our data suggest that the VEGF gene may play a role in the development of RA
View details for DOI 10.1093/rheumatology/keh281
View details for Web of Science ID 000223588600017
View details for PubMedID 15213335
- Stem cell aging and autoimmunity in rheumatoid arthritis TRENDS IN MOLECULAR MEDICINE 2004; 10 (9): 426-433
Tumor necrosis factor-alpha and CD80 modulate CD28 expression through a similar mechanism of T-cell receptor-independent inhibition of transcription
JOURNAL OF BIOLOGICAL CHEMISTRY
2004; 279 (28): 29130-29138
Replicative senescence of human T cells is characterized by the loss of CD28 expression, exemplified by the clonal expansion of CD28(null) T cells during repeated stimulation in vitro as well as in chronic inflammatory and infectious diseases and in the normal course of aging. Because CD28 is the major costimulatory receptor for the induction of T cell-mediated immunity, the mechanism(s) underlying CD28 loss is of paramount interest. Current models of replicative senescence involve protracted procedures to generate CD28(null) cells from CD28(+) precursors; hence, a T-cell line model was used to examine the dynamics of CD28 expression. Here, we show the versatility of the JT and Jtag cell lines in tracking CD28(null) <--> CD28(hi) phenotypic transitions. JT and Jtag cells were CD28(null) and CD28(lo), respectively, but expressed high levels of CD28 when exposed to phorbol 12-myristate 13-acetate. This was a result of the reconstitution of the CD28 gene transcriptional initiator (INR). Tumor necrosis factor-alpha reduced CD28 expression because of the inhibition of INR-driven transcription. Ligation of CD28 by an antibody or by CD80 also down-regulated CD28 transcription through the same mechanism, providing evidence that CD28 can generate a T cell receptor-independent signal with a unique biological outcome. Collectively, these data unequivocally demonstrate the critical role of the INR in the regulation of CD28 expression. T cell lines with transient expression of CD28 are invaluable in the dissection of the biochemical processes involved in the transactivation of the CD28 INR, the silencing of which is a key event in the ontogenesis of senescent T cells.
View details for DOI 10.1074/jbc.M402194200
View details for Web of Science ID 000222445300038
View details for PubMedID 15128741
Lymphotoxin beta-mediated stimulation of synoviocytes in rheumatoid arthritis
ARTHRITIS AND RHEUMATISM
2004; 50 (7): 2140-2150
Lymphotoxin beta (LTbeta), a cytokine produced by T cells and B cells, plays a central role in the normal development of lymph nodes and is critical in the formation of ectopic germinal center reactions in rheumatoid synovitis. Because resident fibroblast-like synoviocytes (FLS) express receptors for LTbeta, we examined the consequences of FLS activation by LTbeta.FLS from patients with rheumatoid arthritis were isolated and examined for the expression of LTbeta receptor. FLS were incubated with LTalpha1beta2 and assayed for the production of cytokines and chemokines and the up-regulation of adhesion molecules.Exposure of FLS to recombinant LTalpha1beta2 resulted in the production of multiple inflammatory cytokines and metalloproteinases, implicating FLS as amplifiers of the inflammatory process in the inflamed joint. Additionally, LTalpha1beta2 was found to up-regulate the expression of cell adhesion molecules, rendering FLS to efficient adhesion substrates for T cells. LTalpha1beta2 also induced production of the chemokines CCL2 and CCL5, which elicited transmigration activity of T cells. Upon stimulation with LTalpha1beta2, FLS did not acquire characteristics of follicular dendritic cells.These data document that FLS are involved in multiple stages of the inflammatory process, including the recruitment and retention of lymphocytes in the synovial microenvironment. We propose that the heterotypic interaction between LTbeta-producing lymphocytes and responding FLS contributes to the establishment of complex lymphoid microstructures, and that this may be one element that defines susceptibility of the synovial membrane to lymphoid organogenesis.
View details for DOI 10.1002/art.20356
View details for Web of Science ID 000222820300012
View details for PubMedID 15248211
T-cell regulation in rheumatoid arthritis
CURRENT OPINION IN RHEUMATOLOGY
2004; 16 (3): 212-217
Rheumatoid arthritis (RA) is characterized by a chronic T-cell response that has escaped normal control mechanisms. This review summarizes recent insights in pathways that are functional in RA and that favor continuous and pathogenic T-cell activation.T-cell activation is ultimately determined by positive signals from costimulatory molecules and negative signals from regulatory T cells. Blockade of the classic costimulatory pathway, CD28-CD80 or CD86, is beneficial in RA. Additional pathways that predominantly control the activation of memory and effector T cells are functionally important in synovial inflammation. Some of these costimulatory molecules (such as stimulatory killer cell immunoglobulin-like receptors and NKG2D) appear to be relatively specific for RA and not to play a role in normal immune responses. In addition to this predominance of positive signals, age-disproportionate decline in thymic activity in RA may lead to a diminution of regulatory T cells and loss of their negative signals.The successful treatment trial of RA with CTLA-4Ig clearly documents the importance of T-cell costimulation in RA disease activity. Novel costimulatory pathways may be of even greater significance than CD28 in RA and may represent promising new therapeutic targets. The finding of reduced thymic activity in RA is exciting and will stimulate further studies of T-cell homeostasis and the function of regulatory cells.
View details for Web of Science ID 000221051800007
View details for PubMedID 15103247
How aggressive should initial therapy for rheumatoid arthritis be? Factors associated with response to 'non-aggressive' DMARD treatment and perspective from a 2-yr open label trial
2004; 43 (5): 619-625
To determine what baseline factors might be associated with response to an initial mild treatment regimen in patients with early rheumatoid arthritis (RA).Open label 2-yr study of 111 consecutive patients with early RA of duration less than 1 yr. None of the patients had previously received disease-modifying anti-rheumatic drugs (DMARDs). All patients were assigned to receive hydroxychloroquine (HCQ) at enrollment, and could also take non-steroidal anti-inflammatory drugs (NSAIDs) and prednisone. At any point during follow-up, patients not fulfilling the American College of Rheumatology (ACR) 50 criteria for improvement and/or who were taking prednisone > 10 mg/day were considered treatment failures and therapy changed to methotrexate (MTX), 7.5-20 mg/week. Clinical, laboratory and immunogenetic factors potentially predictive of treatment assignment at month 24 were evaluated.After 24 months of follow-up, a majority of patients (56/94) were either still on solo DMARD therapy with HCQ (n = 49) or off DMARD therapy with controlled/quiescent disease (n = 4), and 38 patients were taking MTX (including 11 in combination with other DMARDs). At month 24, all but 9 patients met ACR50 criteria for treatment response. Features present at enrollment which were predictors of MTX therapy at month 24 were high pain score, baseline rheumatoid factor titre > 1:40, higher number of swollen joints, and poor patient global assessment. The presence of HLA-C7xx at enrollment was also predictive of need for MTX therapy.This study suggests that even milder treatment with HCQ is greatly beneficial in patients with early RA. There continue to be very few consistently reliable predictors of treatment needs in patients with this disease.
View details for DOI 10.1093/rheumatology/keh135
View details for Web of Science ID 000221297900014
View details for PubMedID 14983105
T-cell senescence: a culprit of immune abnormalities in chronic inflammation and persistent infection
TRENDS IN MOLECULAR MEDICINE
2004; 10 (3): 119-124
Long-lived clonal T cells deficient in CD28 expression are commonly found in patients with inflammatory syndromes and persistent infections. Considering that CD28 loss is the most consistent immunological marker of aging, we propose that, in pathological states, CD28(null) T cells represent prematurely senescent cells resulting from persistent immune activation. These unusual lymphocytes have aberrant functions that contribute to disease-related immune abnormalities, and the degree of accumulation of CD28(null) T cells predicts the severity of clinical manifestations. We suggest that understanding of the biological properties of T cells that have reached replicative senescence will influence the future management of certain diseases. Indeed, studies on the molecular basis for the loss of CD28 are already providing information on methods to functionally rescue senescent T cells.
View details for DOI 10.1016/j.molmed.2004.01.002
View details for Web of Science ID 000220461200010
View details for PubMedID 15102354
Biology of T lymphocytes
RHEUMATIC DISEASE CLINICS OF NORTH AMERICA
2004; 30 (1): 135-?
T cells constitute one arm of the adaptive immune system. The accumulating information on various aspects of T-cell biology shows the intricacies in the regulation of immune responses. How we translate the cellular and molecular details of this regulation into innovation and development of therapies for disease management remains a fundamental, but exciting, challenge.
View details for DOI 10.1016/S0889-857X(03)00114-5
View details for Web of Science ID 000220293300008
View details for PubMedID 15061572
Activation of arterial wall dendritic cells and breakdown of self-tolerance in giant cell arteritis
JOURNAL OF EXPERIMENTAL MEDICINE
2004; 199 (2): 173-183
Giant cell arteritis (GCA) is a granulomatous and occlusive vasculitis that causes blindness, stroke, and aortic aneurysm. CD4(+) T cells are selectively activated in the adventitia of affected arteries. In human GCA artery-severe combined immunodeficiency (SCID) mouse chimeras, depletion of CD83(+) dendritic cells (DCs) abrogated vasculitis, suggesting that DCs are critical antigen-presenting cells in GCA. Healthy medium-size arteries possessed an indigenous population of DCs at the adventitia-media border. Adoptive T cell transfer into temporal artery-SCID mouse chimeras demonstrated that DCs in healthy arteries were functionally immature, but gained T cell stimulatory capacity after injection of lipopolysaccharide. In patients with polymyalgia rheumatica (PMR), a subclinical variant of GCA, adventitial DCs were mature and produced the chemokines CCL19 and CCL21, but vasculitic infiltrates were lacking. Human histocompatibility leukocyte antigen class II-matched healthy arteries, PMR arteries, and GCA arteries were coimplanted into SCID mice. Immature DCs in healthy arteries failed to stimulate T cells, but DCs in PMR arteries could attract, retain, and activate T cells that originated from the GCA lesions. We propose that in situ maturation of DCs in the adventitia is an early event in the pathogenesis of GCA. Activation of adventitial DCs initiates and maintains T cell responses in the artery and breaks tissue tolerance in the perivascular space.
View details for DOI 10.1084/jem.20030850
View details for Web of Science ID 000188369700004
View details for PubMedID 14734523
HLA-DRB1 haplotype did not affect the medium-term results of total knee arthroplasty in patients with rheumatoid arthritis.
2004; 14 (1): 37-42
This study investigated whether the HLA-DRB1 "susceptible allele" (SA) genotype is predictive for total knee arthroplasty (TKA) failure in patients with rheumatoid arthritis (RA). The results of 49 TKAs (30 RA patients) with an average follow-up of 7.9 years (range 5-15 years) were analyzed using a 12-item questionnaire and the Knee Society system. HLA-DRB1 alleles were used to estimate the severity of RA and divide the patients into three categories depending upon the gene dose of SA (SA+/+, SA+/-, and SA-/-). For all three categories, the 12-item questionnaire had significantly improved postoperatively, but without significant difference. We divided the 12 items of the questionnaire into two groups: knee-relevant parameters and general parameters. Patients in all three groups improved similarly in knee-relevant parameters. In contrast, those homozygous for SA (SA+/+) benefited less in general parameters. The average radiolucency score was 1.87 mm, with no difference being detected among the three groups. The HLA-DRB1 genotype did not affect the survival of the knee implants. Overall, patients without the RA-associated HLA gene benefited most from TKA as they improved not only in knee function, but also in parameters of general functional status.
View details for PubMedID 17028803
The double life of NK receptors: stimulation or co-stimulation?
TRENDS IN IMMUNOLOGY
2004; 25 (1): 25-32
Stimulatory killer immunoglobulin-like receptors, NKG2D and stimulatory receptors of the CD94-NKG2 family have duplicity in function. On natural killer (NK) cells, these receptors act as independent and competent recognition units. Stimulatory NK receptors also appear on subsets of effector T cells, particularly those that have replicated extensively. When expressed on T cells, they amplify signals mediated through the T-cell antigen receptor and, thus, function as co-stimulatory, but not direct stimulatory, molecules. One mechanism responsible for this dichotomy is the differential expression of adaptor molecules. This duplicity in function, which is not seen for other co-stimulatory molecules, is responsible for the unique context information provided by the NK receptors, and it could explain their involvement in chronic inflammation and autoimmunity.
View details for DOI 10.1016/j.it.2003.10.011
View details for Web of Science ID 000188431800007
View details for PubMedID 14698281
Immunopathways in giant cell arteritis and polymyalgia rheumatica
2004; 3 (1): 46-53
Giant cell arteritis (GCA), a vasculitis that targets medium- and large-size arteries, is ranked as a medical emergency because of its potential to cause blindness and stroke. The typical lesions, granulomas in the vessel wall, are formed by IFN-gamma-producing CD4+ T cells and macrophages. CD4+ T cells undergo in situ activation in the adventitia, where they interact with indigenous dendritic cells. Tissue injury is mediated by several distinct sets of macrophages that are committed to diverse effector functions. The dominant tissue injury in the media results from oxidative stress and leads to smooth muscle cell apoptosis and nitration of endothelial cells. Macrophage-derived growth factors are instrumental in driving the response-to-injury program of the artery that causes intimal hyperplasia and vessel occlusion. Clinical manifestations are those of tissue ischemia or a syndrome of exuberant systemic inflammation. The vascular and the systemic components of GCA contribute differentially to the disease, leading to distinct clinical phenotypes of this arteritis. Immunologically most interesting is polymyalgia rheumatica, in which the systemic component is combined with aborted vasculitis, suggesting a role for artery-specific tolerance mechanisms.
View details for DOI 10.1016/S1568-9972(03)00064-8
View details for Web of Science ID 000189125500007
View details for PubMedID 14871649
Prognostic markers of radiographic progression in early rheumatoid arthritis
ARTHRITIS AND RHEUMATISM
2004; 50 (1): 43-54
To identify prognostic markers that are predictive of progressive erosive disease in patients with early rheumatoid arthritis (RA).The study involved an inception cohort of 111 consecutive patients with RA and a disease duration of <1 year. Patients were treated according to an algorithm designed to avoid overtreatment of mild disease and to accelerate treatment in patients who had continuous disease activity. Patients were evaluated for the presence of clinical and laboratory disease activity markers. We determined the frequency of CD4+,CD28(null) T cells by flow cytometry, HLA-DRB1 gene polymorphisms by polymerase chain reaction (PCR)/sequencing, and 26 single-nucleotide polymorphisms in 19 candidate genes by multiplex PCR and hybridization to an immobilized probe array. Data were analyzed using proportional odds models to identify prognostic markers predictive of erosive progression over 2 years on serial hand/wrist radiographs.After 2 years, disease activity in 52% of the cohort was controlled by treatment with hydroxychloroquine and nonsteroidal agents. Forty-eight percent of the patients did not develop erosions. Older age, presence of erosions at baseline, presence of rheumatoid factor, rheumatoid factor titer, and HLA-DRB1*04 alleles, particularly homozygosity for HLA-DRB1*04, were univariate predictors of radiographic progression. Promising novel markers were the frequency of CD4+,CD28(null) T cells as an immunosenescence indicator, and a polymorphism in the uteroglobin gene.Clinical disease activity in patients with early RA can frequently be controlled with nonaggressive treatment, but this is not always sufficient to prevent new erosions. Rheumatoid factor titer, HLA-DRB1 polymorphisms, age, and immunosenescence markers are predictors of poor radiographic outcome. A polymorphism in the uteroglobin gene may identify patients who have a low risk of erosive disease.
View details for DOI 10.1002/art.11445
View details for Web of Science ID 000188085600006
View details for PubMedID 14730598
Premature telomeric loss in rheumatoid arthritis is genetically determined and involves both myeloid and lymphoid cell lineages
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2003; 100 (23): 13471-13476
In rheumatoid arthritis, peripheral blood T cells have age-inappropriate telomeric erosion. We examined whether HLA-DRB1*04 alleles, the major susceptibility genes for this disease, confer risk for T cell senescence. In healthy individuals, HLA-DRB1*04 alleles were associated with excessive loss of telomeres in CD4+ T cells. Accelerated telomeric erosion occurred during the first two decades of life and was followed by reduced homeostatic T cell proliferation during adulthood. Premature telomeric loss also affected granulocytes, suggesting that the hematopoietic stem cell is the primary target. Telomeric repair mechanisms were intact in HLA-DRB1*04+ donors. We propose that HLA-DRB1*04 alleles or genes in linkage disequilibrium regulate stem cell replication and contribute to the accumulation of senescent and autoreactive T cells in rheumatoid arthritis.
View details for Web of Science ID 000186573700065
View details for PubMedID 14578453
Giant-cell arteritis and polymyalgia rheumatica
ANNALS OF INTERNAL MEDICINE
2003; 139 (6): 505-515
Giant-cell arteritis is an immune-mediated disease characterized by granulomatous infiltrates in the wall of medium-size and large arteries. The immunopathology consists of 2 components. Excessive cytokine production (for example, of interleukin-1 and interleukin-6) induces systemic inflammation with an exuberant acute-phase response. In parallel, interferon-gamma, which is released by T cells captured in the arterial wall, activates tissue-injurious macrophages. In response to the immune injury, the artery generates hyperplasia of the intima that leads to luminal occlusion and subsequent tissue ischemia. Despite the systemic character of the disease, distinct vascular territories are preferentially affected. On the basis of the predominant involvement, clinical subtypes can be distinguished: cranial giant-cell arteritis with ischemic complications in the eye, the face, and the central nervous system; large-vessel giant-cell arteritis with occlusions in the subclavian or axillary vessels; aortic giant-cell arteritis; giant-cell arteritis presenting as an intense systemic inflammatory syndrome with nonstenosing vasculitis; and "isolated" polymyalgia rheumatica with myalgias, systemic inflammation, and subclinical vasculitis. Temporal artery biopsy remains the diagnostic procedure of choice to detect arteritis in cranial vessels. In other vascular territories, giant-cell arteritis is most commonly diagnosed by vascular imaging. Laboratory studies characteristically document the marked elevations of nonspecific acute-phase reactants, such as C-reactive protein and erythrocyte sedimentation rate. Cytokines, such as interleukin-6, that induce the acute-phase reaction are currently being explored as more sensitive biological markers of disease activity. Corticosteroids are highly effective in suppressing systemic inflammation, but they do not eliminate the immune responses in the vessel wall. In general, the clinical outcome of giant-cell arteritis is excellent, and efforts must now concentrate on tailoring therapies to the needs of the individual patient.
View details for Web of Science ID 000185324100008
View details for PubMedID 13679329
Synoviocyte-mediated expansion of inflammatory T cells in rheumatoid synovitis is dependent on CD47-thrombospondin 1 interaction
JOURNAL OF IMMUNOLOGY
2003; 171 (4): 1732-1740
Fibroblast-like synoviocytes (FLS) from patients with rheumatoid arthritis elicit spontaneous proliferation of autologous T cells in an HLA-DR and CD47 costimulation-dependent manner. T cell costimulation through CD47 is attributed to specific interaction with thrombospondin-1 (TSP1), a CD47 ligand displayed on FLS. CD47 binding by FLS has broad biological impact that includes adhesion and the triggering of specific costimulatory signals. TSP1(+) FLS are highly adhesive to T cells and support their aggregation and growth in situ. Long-term cultures of T cells and FLS form heterotypic foci that are amenable to propagation without exogenous growth factors. T cell adhesion and aggregate formation on TSP1(+) FLS substrates are inhibited by CD47-binding peptides. In contrast, FLS from arthroscopy controls lack adhesive or T cell growth-promoting activities. CD47 stimulation transduces a costimulatory signal different from that of CD28, producing a gene expression profile that included induction of ferritin L chain, a component of the inflammatory response. Ferritin L chain augments CD3-induced proliferation of T cells. Collectively, these results demonstrate the active role of FLS in the recruitment, activation, and expansion of T cells in a CD47-dependent manner. Because TSP1 is abundantly expressed in the rheumatoid synovium, CD47-TSP1 interaction is proposed to be a key component of an FLS/T cell regulatory circuit that perpetuates the inflammatory process in the rheumatoid joint.
View details for Web of Science ID 000184667400018
View details for PubMedID 12902472
Homeostatic control of T-cell generation in neonates
2003; 102 (4): 1428-1434
T cells are produced through 2 mechanisms, thymopoiesis and proliferative expansion of postthymic T cells. Thymic output generates diversity of the pool, and proliferation achieves optimal clonal size of each individual T cell. To determine the contribution of these 2 mechanisms to the formation of the initial T-cell repertoire, we examined neonates of 30 to 40 weeks' gestation. Peripheral T cells were in a state of high proliferative turnover. In premature infants, 10% of T cells were dividing; the proliferation rates then declined but were still elevated in mature newborns. Throughout the third trimester, concentrations of T-cell-receptor excision circles (TRECs) were 10 per 100 T cells. Stability of TREC frequencies throughout the period of repertoire generation suggested strict regulation of clonal size to approximately 10 to 20 cells. Neonatal naive CD4+ and CD8+ T cells were explicitly responsive to IL-7; growth-promoting properties of IL-15 were selective for newborn CD8+ T cells. Neonatal T cells expressed telomerase and, in spite of the high turnover, built up a telomeric reserve. Thus, proliferative expansion, facilitated by increased cytokine responsiveness, and thymopoiesis complement each other as mechanisms of T-cell production in neonates. Maintaining optimal clonal size instead of filling the space in a lymphopenic host appears to regulate homeostatic T-cell proliferation during fetal development.
View details for Web of Science ID 000184651600046
View details for PubMedID 12714521
Immunosenescence, autoimmunity, and rheumatoid arthritis
2003; 38 (8): 833-841
Current disease models of autoimmune syndromes, such as rheumatoid arthritis, propose that chronic inflammation is caused by 'forbidden T-cell clones' that recognize disease-inducing antigens and drive tissue-injurious immune reactions. Reappraisal of disease incidence data, however, emphasizes that rheumatoid arthritis is a syndrome of the elderly that occurs with highest likelihood in individuals in whom the processes of T-cell generation and T-cell repertoire formation are compromised. Thymic T-cell production declines rapidly with advancing age. Multiple mechanisms, including antigen-driven clonal expansion and homeostasis-driven autoproliferation of post-thymic T cells, impose replicative stress on T cells and induce the biological program of cellular senescence. T-cell immunosenescence is associated with profound changes in T-cell functional profile and leads to accumulation of CD4+ T cells that have lost CD28 but have gained killer immunoglobulin-like receptors and cytolytic capability and produce large amounts of interferon-gamma. In patients with rheumatoid arthritis, T-cell immunosenescence occurs prematurely, probably due to a deficiency in the ability to generate sufficient numbers of novel T cells. We propose that autoimmunity in rheumatoid arthritis is a consequence of immunodegeneration that is associated with age-inappropriate remodeling of the T-cell pool.
View details for DOI 10.1016/S0531-5565(03)00090-1
View details for Web of Science ID 000185452800003
View details for PubMedID 12915205
De novo expression of killer immunoglobulin-like receptors and signaling proteins regulates the cytotoxic function of CD4 T cells in acute coronary syndromes
2003; 93 (2): 106-113
The inflammatory infiltrate in atherosclerotic plaque is composed of T cells and macrophages. CD4+ T cells with a unique phenotype, CD4+CD28null, are preferentially recruited into culprit lesions. These T cells are distinct from classic CD4+CD28+ T cells in gene expression and function, including their ability to mediate cytolysis. In this study, we have investigated the regulation of CD4+CD28null T-cell cytolytic function. In patients with acute coronary syndromes (ACS), CD4+CD28null T cells express killer immunoglobulin-like receptors (KIRs). KIRs encompass a polymorphic family of receptors that recognize HLA class I molecules and have been implicated in self-tolerance. CD4+CD28null T-cell clones from patients with ACS and age-matched controls were compared for their KIR-expression profile. T-cell clones derived from the patients expressed a broader spectrum of KIRs (P<0.001) with preference for the stimulatory variant, CD158j. Additionally, CD4+ T-cell clones from patients but not those from controls acquired de novo expression of the DAP12 molecule, an adapter chain that transmits CD158j-derived signals. Cumulative expression of CD158j and DAP12 endowed cytolytic competence on CD4+CD28null T cells, allowing them to kill in the absence of T-cell receptor triggering. Our data demonstrate that CD4+CD28null T cells in ACS are characterized by a unique gene expression profile. Consequently, these T cells acquire cytolytic capability that can bypass the need for T-cell receptor triggering and, thus, impose a threat to self-tolerance.
View details for DOI 10.1161/01.RES.0000082333.58263.58
View details for Web of Science ID 000184346500005
View details for PubMedID 12816883
Medium- and large-vessel vasculitis.
New England journal of medicine
2003; 349 (2): 160-169
View details for PubMedID 12853590
The power of the third dimension: tissue architecture and autoimmunity in rheumatoid arthritis
CURRENT OPINION IN RHEUMATOLOGY
2003; 15 (3): 259-266
Lymphoid organs are the anatomic solution to the challenge of responding to minute amounts of antigen with powerful effector mechanisms. By arranging interacting cells in complex three-dimensional topographies lymphoid organs provide an optimal match between form and function. This principle is exploited in ectopic lymphoid structures that characteristically appear in rheumatoid synovitis. Synovial tissue T cells and B cells cooperate in different types of lymphoid organizations. Dendritic cell networks in the inflamed synovial membrane optimize antigen collection, storage, processing, and presentation. Synovial tissue cells participate in lymphocyte recruitment and the formation of tissue architectures that amplify immune responses. Recent data support the concept that the tissue organization in the rheumatoid joint fosters a breakdown in self-tolerance by promoting a phase transition from self-limited immune responses to self-perpetuating autoimmune responses.
View details for Web of Science ID 000182544200013
View details for PubMedID 12707579
CD28 loss in senescent CD4+ T cells: reversal by interleukin-12 stimulation
2003; 101 (9): 3543-3549
CD28 is the quintessential costimulatory molecule expressed on CD4(+) and CD8(+) T cells. During chronic infections and the normal aging process, CD28 expression is lost, compromising the functional activity of T cells. CD28 loss is promoted by replicative stress, particularly in the presence of tumor necrosis factor-alpha, owing to an inoperative CD28 initiator element. It is currently unknown whether CD28 loss is irreversible. The present study examined cytokines for their ability to reinduce CD28 expression. CD4(+)CD28(null) T cells constitutively expressed interleukin-12 (IL-12) alpha and beta receptors, which were functional and allowed for the up-regulation of the signal transducer and activator of transcription-4 (STAT-4)-dependent gene CD161. Costimulation of the T-cell and IL-12 receptors induced the transcription of CD28 in approximately 50% of CD4(+)CD28(null) T-cell clones and lines. IL-12 by itself did not restore CD28 expression. Up-regulation of CD28 after IL-12 exposure correlated with the reassembly of the CD28-initiator protein complex. The re-expressed CD28 was functional and restored the ability of CD4(+)CD28(null) T cells to express CD25 and CD40 ligand. Our data suggest that IL-12 may, in part, functionally rescue senescent CD4(+) T cells.
View details for DOI 10.1182/blood-2002-08-2574
View details for Web of Science ID 000182625600042
View details for PubMedID 12506015
Selective activation of the c-Jun NH2-terminal protein kinase signaling pathway by stimulatory KIR in the absence of KARAP/DAP12 in CD4(+) T cells
JOURNAL OF EXPERIMENTAL MEDICINE
2003; 197 (4): 437-449
Activation of CD4(+) T cells is governed by interplay between stimulatory and inhibitory receptors; predominance of stimulatory signals favors autoimmune reactions. In patients with rheumatoid arthritis, expression of the critical costimulatory molecule, CD28, is frequently lost. Instead, CD4(+)CD28(null) T cells express killer immunoglobulin-like receptors (KIRs) with a preferential expression of the stimulatory receptor, CD158j. The frequency of CD4(+)CD28(null) T cells in rheumatoid arthritis (RA) correlates with the risk for more severe disease. Moreover, the KIR2DS2 gene, which encodes for CD158j, is a genetic risk factor for rheumatoid vasculitis. CD158j signals through the adaptor molecule, KARAP/DAP12, to positively regulate cytotoxic activity in NK cells. However, the majority of CD4(+)CD28(null) T cell clones lacked the expression of KARAP/DAP12. Despite the absence of KARAP/DAP12, CD158j was functional and augmented interferon-gamma production after T cell receptor stimulation. Cross-linking of CD158j resulted in selective phosphorylation of c-Jun NH(2)-terminal protein kinase (JNK) and its upstream kinase, MKK4 that led to the expression of ATF-2 and c-Jun, all in the absence of extracellular signal-regulated kinase (ERK)1/2 phosphorylation. Mutation of the lysine residue within the transmembrane domain of CD158j abolished JNK activation, suggesting that an alternate adaptor molecule was being used. CD4(+)CD28(null) T cells expressed DAP10 and inhibition of phosphatidylinositol 3-kinase, which acts downstream of DAP10, inhibited JNK activation; however, no interaction of DAP10 with CD158j could be detected. Our data suggest that CD158j in T cells functions as a costimulatory molecule through the JNK pathway independent of KARAP/DAP12 and DAP10. Costimulation by CD158j may contribute to the autoreactivity of CD4(+)CD28(null) T cells in RA.
View details for DOI 10.1084/jem.20020383
View details for Web of Science ID 000181179400005
View details for PubMedID 12591902
Ectopic germinal center formation in rheumatoid synovitis
IMMUNE MECHANISMS AND DISEASE
2003; 987: 140-149
Synovial inflammation in rheumatoid arthritis is closely related to the formation of ectopic lymphoid microstructures. In synovial tissue from some patients, one finds seemingly diffuse infiltrates; in others, T cells and B cells cluster in aggregates with interdigitating dendritic cells (DCs) but no follicular DCs (FDCs). In a third group, T cell/B cell follicles with germinal center (GC) reactions are generated. Within a given patient, aggregates and GCs are mutually exclusive and stable over time. Because antigen storage capacity, lymphoid density, and three-dimensional topography of GCs optimize immune responses, synovial GCs should play a crucial role in the breakdown of self-tolerance. We have identified factors critical for ectopic GCs, thereby transforming the synovial inflammatory process. Tissues with GCs produced 10- to 20-fold higher amounts of the chemokines CXCL13 and CCL21. CXCL13 derived from three sources, endothelial cells, synovial fibroblasts, and FDC networks. The level of CXCL13 transcripts strongly predicted GCs; however, some tissues had high levels of CXCL13 but lacked GCs. Tissue expression of LT-beta emerged as a second key factor. LT-beta protein was detected on follicular center and mantle zone B cells. Multivariate regression analysis identified CXCL13 and LT-beta as the only cytokines predicting GCs. Remarkably, LT-alpha did not contribute independently. The contribution of B cells to ectopic lymphoid organogenesis was not limited to LT-beta production. Rather, synovial tissue B cells were critical in regulating T cell activation. In adoptive transfer experiments in human synovium-SCID mouse chimeras, activation of synovium-derived CD4 T cells was strictly dependent on T cell/B cell follicles. Depletion of synovial tissue B cells abrogated T cell function, and non-B cell antigen-presenting cells could not maintain T cell stimulation. Unexpectedly, GC function in the rheumatoid lesion was also dependent on CD8 T cells. The majority of T cell receptors derived from CD8 T cells were shared between distinct GCs. Depletion of CD8 T cells disrupted synovial GCs, FDC networks disappeared, and transcription of LT-beta, IgG, and Igkappa declined. Follicle-sustaining CD8 T cells were located at the edge of or within the mantle zone. Cell-cell communication in the mantle zone, including CD8 T cells, appears to be critical for ectopic GC formation in rheumatoid synovitis.
View details for Web of Science ID 000183319000016
View details for PubMedID 12727633
Aging, autoimmunity and arthritis: T-cell senescence and contraction of T-cell repertoire diversity - catalysts of autoimmunity and chronic inflammation.
Arthritis research & therapy
2003; 5 (5): 225-234
Rheumatoid arthritis (RA), like many other autoimmune syndromes, is a disease of adults, with the highest incidence rates reported in the elderly. The immune system undergoes profound changes with advancing age that are beginning to be understood and that need to be incorporated into the pathogenetic models of RA. The age-related decline in thymic function causes extensive remodeling of the T-cell system. Age-dependent changes in T-cell homeostasis are accelerated in patients with RA. The repertoire of naive and memory T cells is less diverse, possibly as a result of thymic insufficiency, and it is biased towards autoreactive cells. Presenescent T cells emerge that are resistant to apoptosis and that often expand to large clonal populations. These cells are under the regulatory control of nonconventional costimulatory molecules, display potent effector functions, and appear to be critical in the synovial and extra-articular manifestations of RA.
View details for PubMedID 12932282
B cells as a therapeutic target in autoimmune disease
ARTHRITIS RESEARCH & THERAPY
2003; 5 (3): 131-135
Depleting B cells with anti-CD20 monoclonal antibodies emerges as a new therapeutic strategy in autoimmune diseases. Preliminary clinical studies suggest therapeutic benefits in patients with classic autoantibody-mediated syndromes, such as autoimmune cytopenias. Treatment responses in rheumatoid arthritis have opened the discussion about whether mechanisms beyond the removal of potentially pathogenic antibodies are effective in B-cell depletion. B cells may modulate T-cell activity through capturing and presenting antigens or may participate in the neogenesis of lymphoid microstructures that amplify and deviate immune responses. Studies exploring which mechanisms are functional in which subset of patients hold the promise of providing new and rational treatment approaches for autoimmune syndromes.
View details for DOI 10.1186/ar751
View details for Web of Science ID 000182395200010
View details for PubMedID 12723978
Molecular basis for the loss of CD28 expression in senescent T cells
JOURNAL OF BIOLOGICAL CHEMISTRY
2002; 277 (49): 46940-46949
CD28(null) T cells are the most consistent biological indicator of the aging immune system in humans and are predictors of immunoincompetence in the elderly. The loss of CD28 is the result of an inoperative transcriptional initiator (INR), which consists of two nonoverlapping alpha and beta motifs that have distinct protein binding profiles but function as a unit. In CD28(null) T cells, there is a coordinate loss of alpha-/beta-bound complexes, hence the alphabeta-INR is inactive. In the present work therefore, studies were conducted to identify the components of such complexes that may account for the trans-activation of the alphabeta-INR. By affinity chromatography and tandem mass spectrometry, two proteins, namely, nucleolin and the A isoform of heterogeneous nuclear ribonucleoprotein-D0 (hnRNP-D0A), were identified to be among the key components of the site alpha complex. In DNA binding assays, specific antibodies indicated their antigenic presence in alpha-bound complexes. Transcription assays showed that they are both required in the trans-activation of alphabeta-INR-driven DNA templates. Because CD28 is T cell-restricted, and nucleolin and hnRNP-D0A are ubiquitous proteins, these results support the notion that cell-specific functions can be regulated by commonly expressed proteins. The present data also provide evidence for INR-regulated transcription that is independent of the known components of the basal transcription complex.
View details for DOI 10.1074/jbc.M207352200
View details for Web of Science ID 000179663700015
View details for PubMedID 12324461
Trapping of misdirected dendritic cells in the granulomatous lesions of giant cell arteritis
AMERICAN JOURNAL OF PATHOLOGY
2002; 161 (5): 1815-1823
Immature dendritic cells (DCs) are scattered throughout peripheral tissues and act as sentinels that sample the antigenic environment. After activation, they modify their chemokine receptor profile and migrate toward lymphoid tissues. On arrival, they have matured into chemokine-producing DCs that express co-stimulatory molecules and can prime naive T cells. Normal temporal arteries contain immature DCs that are located at the media-adventitia border. In temporal arteries affected by giant cell arteritis, DCs are highly enriched and activated and have matured into fully differentiated cells producing the chemokines, CCL18, CCL19, and CCL21. In keeping with their advanced maturation, DCs in the granulomatous lesions possess the chemokine receptor, CCR7. CCR7 binds CCL19 and CCL21, causing the highly activated DCs to be trapped in the peripheral tissue site. The co-stimulatory molecule, CD86, which is critical for DC/T-cell interaction, is expressed by a subset of DCs captured in the arterial wall. DC/T-cell interaction does not involve interleukin-12; transcripts for interleukin-12 p40 are absent in the vasculitic infiltrates. We propose that differentiation of DCs and the autocrine and paracrine actions of chemokines in granulomatous lesions misdirect DCs away from their usual journey to lymphoid organs and are critical in maintaining T-cell activation and granuloma formation in giant cell arteritis.
View details for Web of Science ID 000179197000030
View details for PubMedID 12414528
Reactive nitrogen intermediates in giant cell arteritis - Selective nitration of neocapillaries
AMERICAN JOURNAL OF PATHOLOGY
2002; 161 (1): 115-123
Arterial wall damage in giant cell arteritis (GCA) is mediated by several different macrophage effector functions, including the production of metalloproteinases and lipid peroxidation. Tissue-invading macrophages also express nitric oxide synthase (NOS)-2, but it is not known whether nitric oxide-related mechanisms contribute to the disease process. Nitric oxide can form nitrating agents, including peroxynitrite, a nitric oxide congener formed in the presence of reactive oxygen intermediates. Protein nitration selectively targets tyrosine residues and can result in a gain, as well as a loss, of protein function. Nitrated tyrosine residues in GCA arteries were detected almost exclusively on endothelial cells of newly formed microcapillaries in the media, whereas microvessels in the adventitia and the intima were spared. Nitration correlated with endothelial NOS-3 expression and not with NOS-2-producing macrophages, which preferentially homed to the hyperplastic intima. The restriction of nitration to the media coincided with the production of reactive oxygen intermediates as demonstrated by the presence of the toxic aldehyde, 4-hydroxynonenal. Depletion of tissue-infiltrating macrophages in human temporal artery-SCID mouse chimeras disrupted nitrotyrosine generation, demonstrating a critical role of macrophages in the nitration process that targeted medial microvessels. Thus, protein nitration in GCA is highly compartmentalized, reflecting the production of reactive oxygen and reactive nitrogen intermediates in the inflamed arterial wall. Heterogeneity of microvessels in NOS-3 regulation may be an additional determinant contributing to this compartmentalization and could explain the preferential targeting of newly generated capillary beds.
View details for Web of Science ID 000176718300015
View details for PubMedID 12107096
The Ogryzlo Day Lecture - Premature immunosenescence in rheumatoid arthritis - Presented at the University of Toronto Rheumatic Disease Unit Annual Ogryzlo Research Day, June 26, 2001
JOURNAL OF RHEUMATOLOGY
2002; 29 (6): 1141-1146
View details for Web of Science ID 000176033500006
CD8 T cells are required for the formation of ectopic germinal centers in rheumatoid synovitis
JOURNAL OF EXPERIMENTAL MEDICINE
2002; 195 (10): 1325-1336
The assembly of inflammatory lesions in rheumatoid arthritis is highly regulated and typically leads to the formation of lymphoid follicles with germinal center (GC) reactions. We used microdissection of such extranodal follicles to analyze the colonizing T cells. Although the repertoire of follicular T cells was diverse, a subset of T cell receptor (TCR) sequences was detected in multiple independent follicles and not in interfollicular zones, suggesting recognition of a common antigen. Unexpectedly, the majority of shared TCR sequences were from CD8 T cells that were highly enriched in the synovium and present in low numbers in the periphery. To examine their role in extranodal GC reactions, CD8 T cells were depleted in human synovium-SCID mouse chimeras. Depletion of synovial CD8 T cells caused disintegration of the GC-containing follicles. In the absence of CD8 T cells, follicular dendritic cells disappeared, production of lymphotoxin-alpha1beta2 markedly decreased, and immunoglobulin (Ig) secretion ceased. Immunohistochemical studies demonstrated that these CD8 T cells accumulated at the edge of the mantle zone. Besides their unique localization, they were characterized by the production of interferon (IFN)-gamma, lack of the pore-forming enzyme perforin, and expression of CD40 ligand. Perifollicular IFN-gamma+ CD8 T cells were rare in secondary lymphoid tissues but accounted for the majority of IFN-gamma+ cells in synovial infiltrates. We propose that CD8+ T cells regulate the structural integrity and functional activity of GCs in ectopic lymphoid follicles.
View details for DOI 10.1084/jem.20011565
View details for Web of Science ID 000176110900009
View details for PubMedID 12021312
Human leukocyte antigen class II immune response genes, female gender, and cigarette smoking as risk and modulating factors in abdominal aortic aneurysms
JOURNAL OF VASCULAR SURGERY
2002; 35 (5): 988-993
Aortic inflammation and the genes that regulate the immune response play an important role in abdominal aortic aneurysm pathogenesis. However, the modulating effects of such genetic and other environmental factors on the severity on aneurysm inflammation is not known. The objective of this study was to determine the influence of the human leukocyte antigen (HLA) class II genes, gender, and environmental factors on degree of abdominal aortic aneurysm tissue inflammation.Aneurysm specimens were obtained at the time of operation from 96 consecutive patients who underwent abdominal aortic aneurysm repair and were graded for degree of histologic inflammation. Multivariate analysis was used to determine the association of genetic and environmental factors with degree of inflammation and to determine the HLA-associated disease risk for aneurysm.Active cigarette smoking and female gender were independently associated with high-grade tissue inflammation identified histologically (odds ratio [OR], confidence interval [CI]: 5.6, 1.6 to 19.3; and 6.0, 1.4 to 26.2, respectively), and a specific HLA allele (DR B1(*)01) was inversely associated with inflammation (OR, CI: 0.2, 0.04 to 0.7). Overall, the HLA-DR B1(*)02 and B1(*)04 alleles were significantly associated with disease risk, more than doubling risk for abdominal aortic aneurysm (OR, CI: 2.5, 1.4 to 4.3; and 2.1, 1.2 to 3.7, respectively).Active cigarette smoking and female gender are significant disease-modulating factors associated with increased abdominal aortic aneurysm inflammation. In addition, the HLA class II immune response genes possess both disease modulating and disease risk properties, which may be useful in early aneurysm detection and surveillance.
View details for DOI 10.1067/mva.2002.121753
View details for Web of Science ID 000175919100034
View details for PubMedID 12021716
Formation of the killer Ig-like receptor repertoire on CD4(+)CD28(null) T cells
JOURNAL OF IMMUNOLOGY
2002; 168 (8): 3839-3846
Killer Ig-like receptors (KIRs) are expressed on CD4(+)CD28(null) T cells, a highly oligoclonal subset of T cells that is expanded in patients with rheumatoid arthritis. It is unclear at what stage of development these T cells acquire KIR expression. To determine whether KIR expression is a consequence of clonal expansion and replicative senescence, multiple CD4(+)CD28(null) T cell clones expressing the in vivo dominant TCR beta-chain sequences were identified in three patients and analyzed for their KIR gene expression pattern. Based on sharing of TCR sequences, the clones were grouped into five clone families. The repertoire of KIRs was diverse, even within each clone family; however, the gene expression was not random. Three particular receptors, KIR2DS2, KIR2DL2, and KIR3DL2, had significant differences in gene expression frequencies between the clone families. These data suggest that KIRs are successively acquired after TCR rearrangement, with each clone family developing a dominant expression pattern. The patterns did not segregate with the individual from whom the clones were derived, indicating that peripheral selection in the host environment was not a major shaping force. Several models were examined using a computer algorithm that was designed to simulate the expression of KIRs at various times during T cell proliferation. The computer simulations favored a model in which KIR gene expression is inducible for a limited time during the initial stages of clonal expansion.
View details for Web of Science ID 000174913300022
View details for PubMedID 11937537
T-cell-mediated lysis of endothelial cells in acute coronary syndromes
2002; 105 (5): 570-575
CD4 T lymphocytes accumulate in unstable plaque. The direct and indirect involvement of these T cells in tissue injury and plaque instability is not understood.Gene profiling identified perforin, CD161, and members of the killer-cell immunoglobulin-like receptors as being differentially expressed in CD4(+)CD28(null) T cells, a T-cell subset that preferentially infiltrates unstable plaque. Frequencies of CD161(+) and perforin-expressing CD4 T cells in peripheral blood were significantly increased in patients with unstable angina (UA). CD161 appeared on CD4(+)CD28(null) T cells after stimulation, suggesting spontaneous activation of circulating CD4 T cells in UA. Perforin-expressing CD4(+) T-cell clones from patients with UA exhibited cytotoxic activity against human umbilical vein endothelial cells (HUVECs) in redirected cytotoxicity assays after T-cell receptor triggering and also after stimulation of major histocompatibility complex class I-recognizing killer-cell immunoglobulin-like receptors. HUVEC cytolysis was dependent on granule exocytosis, as demonstrated by the paralyzing effect of pretreating CD4(+)CD28(null) T cells with strontium. Incubation of HUVECs with C-reactive protein (CRP) increased HUVEC lysis in a dose-dependent fashion.In patients with UA, CD4 T cells undergo a change in functional profile and acquire cytotoxic capability. Cytotoxic CD4 T cells effectively kill endothelial cells; CRP sensitizes endothelial cells to the cytotoxic process. We propose that T-cell-mediated endothelial cell injury is a novel pathway of tissue damage that contributes to plaque destabilization. The sensitizing effect of CRP suggests synergy between dysregulated T-cell function and acute phase proteins in acute coronary syndromes.
View details for Web of Science ID 000173735400022
View details for PubMedID 11827921
Therapeutic effects of acetylsalicylic acid in giant cell arteritis
ARTHRITIS AND RHEUMATISM
2002; 46 (2): 457-466
In giant cell arteritis (GCA), inflammatory lesions typically produce interferon-gamma(IFNgamma)-- and nuclear factor kappaB (NF-kappaB)-dependent monokines. Corticosteroids influence disease activity by repressing NF-kappaB-dependent genes but have only marginal effects on IFNgamma. The current study explored whether acetylsalicylic acid (ASA) had cytokine-repressing activity in GCA and could function as a steroid-sparing agent.Temporal artery-severe combined immunodeficiency (SCID) mouse chimeras were created by engrafting inflamed temporal arteries into SCID mice. Chimeras were treated with ASA, indomethacin, or dexamethasone for 3 weeks. Temporal artery grafts were harvested and cytokine message was semiquantified by polymerase chain reaction-enzyme-linked immunosorbent assay. The ability of dexamethasone and ASA to suppress IFNgamma and interleukin-1beta (IL-1beta) messenger RNA and protein production was also tested in vitro using T cell clones and monocytes derived from patients with GCA. Drug-induced effects on the transcription factors NF-kappaB and activator protein 1 (AP-1) were assessed by electrophoretic mobility shift assays (EMSAs).At clinically relevant doses, 20-100 mg/kg, ASA was a highly effective inhibitor of cytokine transcription in temporal arteries. While dexamethasone preferentially targeted NF-kappaB-regulated monokines, ASA acted predominantly by suppressing IFNgamma. Indomethacin failed to reduce tissue IFNgamma transcription, which therefore excluded the inhibition of cyclooxygenases as a critical mechanism. IFNgamma production by T cell clones was highly sensitive to ASA-mediated suppression, whereas IL-1beta production by lipopolysaccharide-stimulated monocytes responded primarily to dexamethasone. The combination of ASA and dexamethasone had synergistic effects. EMSAs demonstrated that ASA interfered with the formation of AP-1, whereas dexamethasone suppressed the nuclear translocation of NF-kappaB.The results of this study provide evidence of the complementary action of ASA and corticosteroids in suppressing proinflammatory cytokines in the vascular lesions of GCA.
View details for Web of Science ID 000173785800021
View details for PubMedID 11840449
Pathogenic mechanisms in giant cell arteritis.
Cleveland Clinic journal of medicine
2002; 69: SII28-32
T lymphocytes, encountering stimulatory signals in the adventitia of medium-size arteries, emerge as the key players in inflammation-associated injury pathways. In GCA, all injury mechanisms have been related to effector macrophages. Regulated by IFN-gamma-producing T cells, macrophages commit to distinct avenues of differentiation and acquire a spectrum of potentially harmful capabilities (Figure 1). Macrophages in the adventitia focus on production of pro-inflammatory cytokines. Macrophages in the media specialize in oxidative damage with lipid peroxidation attacking smooth muscle cells and matrix components. These macrophages also supply reactive oxygen intermediates that, in combination with nitrogen intermediates, cause protein nitration of endothelial cells. Production of oxygen radicals is complemented by the production of metalloproteinases, likely essential in the breakdown of elastic membranes. With the fragmentation of the internal elastic lamina, the intimal layer becomes accessible to migratory myofibroblasts that, driven by PDGF, form a hyperplastic intimal layer and cause occlusion of the vessel lumen. Expansion of the hyperplastic intima is accompanied by intense neoangiogenesis, supported by angiogenesis factors that again derive from specialized macrophages. Similarities in injury pathways between GCA and another arterial disease, atherosclerosis, are beginning to be recognized. Specifically, activated T cells and macrophages are increasingly appreciated as key players in the process of instability and rupture of atherosclerotic plaque. A specialized subset of CD4 T cells, CD4+ CD28- T cells, are suspected to participate in tissue injury in the plaque. These T cells are equipped with cytolytic capabilities and release large amounts of IFN-gamma. Comparative studies between patients with GCA and those with acute coronary syndromes should enhance our ability to define the principles of arterial wall inflammation, the specifics of injury in that microenvironment, and help in the identification of the eliciting signals.
View details for PubMedID 12086261
Cytokines in giant-cell arteritis.
Cleveland Clinic journal of medicine
2002; 69: SII91-4
Cytokines are small proteins that serve as chemical messengers between cells, regulating cell growth and differentiation, tissue repair and remodeling, and many aspects of the immune response. Cytokines are instrumental in determining the nature, magnitude, and duration of inflammatory reactions and, as such, represent ideal targets for interfering with pathogenic processes. In OCA and PMR, cytokines are encountered in two locations, the inflammatory infiltrates accumulating in the arterial wall and in the circulation. IL-6, a cytokine involved in stimulating acute-phase responses, is located upstream of many of the laboratory abnormalities considered helpful in diagnosing and managing GCA/PMR, including elevated ESR and CRP. IL-6 has the potential to be helpful in predicting disease severity and may allow for a tailoring of immunosuppressive therapy. There is evidence suggesting that IL-6 outperforms other chemical markers in detecting disease activity and could, therefore, have a role in monitoring treatment. Interesting pathogenic clues have been derived from studies of cytokines produced in the vascular lesions. IFN-gamma has emerged as a key regulator in determining the nature and direction of the inflammatory response. IFN-gamma appears to be critically involved in modulating the process of intimal hyperplasia, the most destructive consequence of vasculitis, and, as such, emerges as a prime target for novel therapeutic approaches.
View details for PubMedID 12086274
Bi-directional modulation of T cell-dependent antibody production by prostaglandin E-2
2002; 14 (1): 69-77
T cell-dependent Ig production involves interaction between T cells and B cells. This study evaluated the effects of prostaglandin (PG) E(2) on Ig production in a system in which B cells were co-cultured with autologous CD4(+) T cell clones non-specifically activated by anti-CD3. The effects of PGE(2) on T cell-dependent Ig production differed substantially, depending on the T cells employed. We selected six T cell clones that were able to enhance Ig production (resistant T cell clones) and six T cell clones that inhibited Ig production in the presence of PGE(2) (sensitive T cell clones) for comparison. The resistant T cells produced high levels (>1000 pg/ml) of IL-2 and/or IL-4, and expressed high CD40L, OX40 and CD45RA, and low CD45RO. In contrast, sensitive T cells secreted low IL-2 (<500 pg/ml) and IL-4 (<200 pg/ml), and expressed low CD40, OX40 and CD45RA, and high CD45RO. Adding supernatant derived from resistant T cell clones restored Ig production inhibited by PGE(2), while removing IL-2, IL-4 or IL-10 using specific antibodies inhibited Ig production. In addition, we demonstrated a direct effect of PGE(2) on B cells to enhance Ig production. Consistently, in the presence of resistant T cells, PGE(2) increased B cell proliferation and differentiation. In conclusion, the effects of PGE(2) on Ig production consist of its indirect effects through T cells and its direct effects on B cells. The outcome of the effects can be up-regulatory or down-regulatory, depending whether resistant or sensitive T cells are involved.
View details for Web of Science ID 000173387200009
View details for PubMedID 11751754
Value of immunological markers in predicting responsiveness to influenza vaccination in elderly individuals
JOURNAL OF VIROLOGY
2001; 75 (24): 12182-12187
Elderly individuals are at high risk for morbidity and mortality when infected with influenza virus. Vaccinations with inactivated virus are less effective in the elderly due to the declining competency of the aging immune system. We have explored whether immunological parameters predict poor anti-influenza virus vaccine responses and can be used as biological markers of immunosenescence. One hundred fifty-three residents of community-based retirement facilities aged 65 to 98 years received a trivalent influenza vaccine. Vaccine-induced antibody responses were determined by comparing hemagglutination inhibition titers before and 28 days after immunization. The composition of the T-cell compartment was analyzed by flow cytometry and the sizes of three T-cell subsets, CD4(+) CD45RO(+) cells, CD4(+) CD28(null) cells, and CD8(+) CD28(null) cells, were determined. Only 17% of the vaccine recipients were able to generate an increase in titers of antibody to all three vaccine components, and 46% of the immunized individuals failed to respond to any of the three hemagglutinins. The likelihood of successful vaccination declined with age and was independently correlated with the expansion of a particular T-cell subset, CD8(+) CD28(null) T cells. The sizes of the CD4(+) CD45RO(+) memory T-cell and CD4(+) CD28(null) T-cell subsets had no effect on the ability to mount anti-influenza virus antibody responses. Frequencies of CD8(+) CD28(null) T cells are useful biological markers of compromised immunocompetence, identifying individuals at risk for insufficient antibody responses.
View details for Web of Science ID 000172355300026
View details for PubMedID 11711609
T cell activation in rheumatoid synovium is B cell dependent
JOURNAL OF IMMUNOLOGY
2001; 167 (8): 4710-4718
Rheumatoid arthritis results from a T cell-driven inflammation in the synovial membrane that is frequently associated with the formation of tertiary lymphoid structures. The significance of this extranodal lymphoid neogenesis is unknown. Microdissection was used to isolate CD4 T cells residing in synovial tissue T cell/B cell follicles. CD4 T cells with identical TCR sequences were represented in independent, nonadjacent follicles, suggesting recognition of the same Ag in different germinal centers. When adoptively transferred into rheumatoid arthritis synovium-SCID mouse chimeras, these CD4 T cell clones enhanced the production of IFN-gamma, IL-1beta, and TNF-alpha. In vivo activity of adoptively transferred CD4 T cells required matching of HLA-DRB1 alleles and also the presence of T cell/B cell follicles. HLA-DRB1-matched synovial tissues that were infiltrated by T cells, macrophages, and dendritic cells, but that lacked B cells, did not support the activation of adoptively transferred CD4 T cell clones, raising the possibility that B cells provided a critical function in T cell activation or harbored the relevant Ag. Dependence of T cell activation on B cells was confirmed in B cell depletion studies. Treatment of chimeric mice with anti-CD20 mAb inhibited the production of IFN-gamma and IL-1beta, indicating that APCs other than B cells could not substitute in maintaining T cell activation. The central role of B cells in synovial inflammation identifies them as excellent targets for immunosuppressive therapy.
View details for Web of Science ID 000171858300071
View details for PubMedID 11591802
T-cell immunity in acute coronary syndromes
MAYO CLINIC PROCEEDINGS
2001; 76 (10): 1011-1020
Acute coronary syndromes (ACS) are complications of atherosclerotic vascular disease that are triggered by the sudden rupture of an atheroma. Atherosclerotic plaque stability is determined by multiple factors, of which immune and inflammatory pathways are critical. Unstable plaque is characterized by an infiltrate of T cells and macrophages, thereby resembling a delayed hypersensitivity reaction. On activation, T cells secrete cytokines that regulate the activity of macrophages, or the T cells may differentiate into effector cells with tissue-damaging potential. Constitutive stimulation of T cells and macrophages in ACS is not limited to the vascular lesion but also involves peripheral immune cells, suggesting fundamental abnormalities in homeostatic mechanisms that control the assembly, turnover, and diversity of the immune system as a whole. This review gives particular attention to the emergence of a specialized T-cell subset, natural killer T cells, in patients with ACS. Natural killer T cells have proinflammatory properties and the capability of directly contributing to vascular injury.
View details for Web of Science ID 000171341900009
View details for PubMedID 11605685
Down-regulation of CD28 expression by TNF-alpha
JOURNAL OF IMMUNOLOGY
2001; 167 (6): 3231-3238
Aging and chronic inflammatory syndromes, such as rheumatoid arthritis, are associated with high frequencies of CD4(+)CD28(null) T cells, which are rarely seen in healthy individuals younger than 40 years. Inasmuch as rheumatoid arthritis and aging are also associated with elevated levels of TNF-alpha, we examined whether this proinflammatory cytokine influences CD28 expression. Incubation of T cell lines and clones as well as Jurkat cells with TNF-alpha induced a reduction in the levels of cell surface expression of CD28. This effect of TNF-alpha was reversible; however, continuous culture of CD4(+)CD28(+) T cell clones in TNF-alpha resulted in the appearance of a CD28(null) subset. In reporter gene bioassays, TNF-alpha was found to inhibit the activity of the CD28 minimal promoter. Inactivation of the promoter was accompanied by a marked reduction in DNA-protein complex formation by two DNA sequence motifs corresponding to the transcriptional initiator of the CD28 gene. Indeed, in vitro transcription assays showed that nuclear extracts from TNF-alpha-treated cells failed to activate transcription of DNA templates under the control of a consensus TATA box and the CD28 initiator sequences. In contrast, similar extracts from unstimulated T cells supported transcription. These results demonstrate that TNF-alpha directly influences CD28 gene transcription. We propose that the emergence of CD4(+)CD28(null) T cells in vivo is facilitated by increased production of TNF-alpha.
View details for Web of Science ID 000172392000027
View details for PubMedID 11544310
- Ectopic lymphoid organogenesis - A fast track for autoimmunity AMERICAN JOURNAL OF PATHOLOGY 2001; 159 (3): 787-793
Lymphoid neogenesis in rheumatoid synovitis
JOURNAL OF IMMUNOLOGY
2001; 167 (2): 1072-1080
In rheumatoid arthritis (RA), tissue-infiltrating lymphocytes can be arranged in sophisticated organizations that resemble microstructures usually formed in secondary lymphoid organs. Molecular pathways and host risk factors involved in this process of lymphoid neogenesis remain to be defined. In a series of 64 synovial tissue biopsies, lymphoid follicles with germinal centers (GCs) were found in 23.4% of the patients. Follicular dendritic cells (FDCs) were exclusively present in tissues with GCs, suggesting that the recruitment or in situ maturation of FDCs is a critical factor for GC formation in the synovial membrane. Primary follicles were absent, emphasizing the role of Ag recognition in the generation of inflammation-associated lymphoid organogenesis. Multivariate logistic regression analysis of tissue cytokines and chemokines identified two parameters, in situ transcription of lymphotoxin (LT)-beta and of B lymphocyte chemoattractant (BLC; BLC/CXCL13), that were predictors for FDC recruitment and synovial GC formation. LT-beta and BLC/CXCL13 were found to be independent variables that could, in part, compensate for each other to facilitate GC formation. Prediction models incorporating in situ transcription of LT-beta and BLC/CXCL13 had high negative yet moderate positive predictive values, suggesting that LT-beta and BLC/CXCL13 are necessary but not sufficient. LT-beta protein was detected on a subset of mantle zone and GC B cells, but also on T cells in follicular structures. BLC/CXCL13 was produced by FDCs in follicular centers, but was predominantly found in endothelial cells and synovial fibroblasts, suggesting heterotypic signaling between cells of the synovial membrane and infiltrating lymphocytes in regulating extranodal lymphoid neogenesis.
View details for Web of Science ID 000170949300058
View details for PubMedID 11441118
Genetic similarity in inflammatory and degenerative abdominal aortic aneurysms: A study of human leukocyte antigen class II disease risk genes
MOSBY-ELSEVIER. 2001: 84-88
Clinically, abdominal aortic aneurysms (AAAs) display a spectrum of inflammation that extends from apparently noninflamed (degenerative) AAAs to the classic inflammatory variant. Genes encoded in the human leukocyte antigen (HLA) region are important in the development of both variants of AAA; however, their role in progression to the inflammatory variant is unknown. The purpose of this study was to compare HLA class II genes in patients with degenerative versus classic inflammatory AAAs and to quantify their impact as disease risk factors.Genotypes of the 12 major alleles of the HLA-DR B1 locus were determined in patients with degenerative (102) and inflammatory (40) AAAs who were compared with controls (118). Univariate and multivariate logistic regression analyses were used to determine allele distributions and to quantify disease risk.Distribution of the HLA-DR B1 alleles was nonrandom and similar in both degenerative and inflammatory AAA groups compared with controls. The B1*02 and B1*04 alleles were enhanced in both degenerative (39.2% vs. 25.4%, P =.03; and 35.3% vs. 24.6%, P =.08 respectively) and inflammatory (47.5% vs. 25.4%, P =.01; and 32.5% vs. 24.6%, P =.09, respectively) AAAs compared with controls. The B1*02 and B1*04 alleles were associated with risk for both degenerative (odds ratio [OR] 2.2; 95% CI, 1.2-4.0; and OR 2.0; 95% CI, 1.1-3.7, respectively) and inflammatory AAAs (OR 3.7; 95% CI, 1.8-8.6; and OR 2.5; 95% CI, 1.1-6.1).This study demonstrates that identical HLA alleles function as genetic risk factors for both inflammatory and degenerative AAAs. These results support the concept of a common, immune-mediated pathogenesis for AAAs that may be modulated by HLA-independent factors.
View details for Web of Science ID 000169840000026
View details for PubMedID 11436079
Major histocompatibility complex class I-recognizing receptors are disease risk genes in rheumatoid arthritis
JOURNAL OF EXPERIMENTAL MEDICINE
2001; 193 (10): 1159-1167
Rheumatoid arthritis (RA) is a heterogeneous syndrome of which a subset of patients develops vascular inflammation. The genetic determinants that confer risk for rheumatoid vasculitis are not known, but patients with vascular complications are known to have an expansion of CD4(+)CD28(null) T cells, a cell population potentially involved in endothelial damage. CD4(+)CD28(null) T cell clones isolated from RA patients with vasculitis were found to express killer cell immunoglobulin-like receptors (KIRs) with the stimulatory KIR2DS2 often present in the absence of opposing inhibitory receptors with related specificities. To test the hypothesis that the KIR2DS2 gene is involved in the development of vasculitis, association studies were performed. The KIR2DS2 gene was significantly enriched among patients with rheumatoid vasculitis compared with normal individuals (odds ratio 5.56, P = 0.001) and patients with RA but no vasculitis (odds ratio 7.96, P = 0.001). Also, the distribution of human histocompatibility leukocyte antigen (HLA)-C, the putative ligand for KIRs, was significantly different in patients with rheumatoid vasculitis in comparison with the control populations. These data suggest that HLA class I-recognizing receptors and HLA class I genes are genetic risk determinants that modulate the pattern of RA expression. Specifically, KIR2DS2 in conjunction with the appropriate HLA-C ligand may have a role in vascular damage by regulating CD4(+)CD28(null) T cells.
View details for Web of Science ID 000169115200006
View details for PubMedID 11369787
Thymic function and peripheral T-cell homeostasis in rheumatoid arthritis
TRENDS IN IMMUNOLOGY
2001; 22 (5): 251-255
T-cell diversity is generated through the production of new thymic emigrants. Thymic function declines with age, and the T-cell pool is maintained through homeostatic proliferation of naive peripheral T cells. This article discusses the impact of thymic output and peripheral T-cell homeostasis on the development of rheumatoid arthritis (RA). It is proposed that thymic output is prematurely compromised in RA patients. A compensatory expansion of peripheral T cells results in a contracted and distorted repertoire, possibly favoring T cells with autoreactive potential. Increased risk of autoimmunity, as a consequence of abnormal T-cell population dynamics, could be a common mechanism in chronic inflammatory diseases.
View details for Web of Science ID 000169936400011
View details for PubMedID 11323282
Molecular fingerprint of interferon-gamma signaling in unstable angina
2001; 103 (11): 1509-1514
Activation of circulating monocytes in patients with acute coronary syndromes may reflect exposure to bacterial products or stimulation by cytokines such as IFN-gamma. IFN-gamma induces phosphorylation and nuclear translocation of transcription factor STAT-1, which initiates a specific program of gene induction. To explore whether monocyte activation is IFN-gamma driven, patients with unstable (UA) or stable angina (SA) were compared for nuclear translocation of STAT-1 complexes and upregulation of IFN-gamma-inducible genes CD64 and IP-10.Peripheral blood mononuclear cells were stained for expression of CD64 on CD14(+) monocytes and analyzed by PCR for transcription of IP-10. Expression of CD64 was significantly increased in patients with UA. Monocytes from UA patients remained responsive to IFN-gamma in vitro, with accelerated transcriptional competency of CD64. IP-10-specific sequences were spontaneously detectable in 82% of the UA patients and 15% of SA patients (P<0.001). Most importantly, STAT-1 complexes were found in nuclear extracts prepared from freshly isolated monocytes of patients with UA, which provides compelling evidence for IFN-gamma signaling in vivo.Monocytes from UA patients exhibit a molecular fingerprint of recent IFN-gamma triggering, such as nuclear translocation of STAT-1 complexes and upregulation of IFN-gamma-inducible genes CD64 and IP-10, which suggests that monocytes are activated, at least in part, by IFN-gamma. IFN-gamma may derive from stimulated T lymphocytes, which implicates specific immune responses in the pathogenesis of acute coronary syndromes.
View details for Web of Science ID 000167636800006
View details for PubMedID 11257077
Functional disruption of the CD28 gene transcriptional initiator in senescent T cells
JOURNAL OF BIOLOGICAL CHEMISTRY
2001; 276 (4): 2565-2570
We recently reported that aging is accompanied by the emergence of CD4(+)CD28(null) T cells, a functionally aberrant lymphocyte subset rarely seen in individuals younger than 40 years. Here, we directly examined whether the lack of CD28 expression is due to a defect at the level of transcriptional initiation. Molecular studies reveal that CD28 gene transcription is controlled by two sequence motifs, sites alpha and beta. In vitro transcription assays using initiator-dependent DNA templates revealed that reversed polarity or the deletion of either motif inhibited transcription, indicating that alpha/beta sequences constitute a composite initiator. Moreover, nuclear extracts from CD28(null) cells failed to activate transcription of alphabeta-initiator DNA templates. Transcription of such templates was, however, restored with the addition of extracts from CD28(+) cells. Although previously described initiator elements have been defined by a consensus sequence, the alphabeta-initiator has no homology to such sequence. These studies demonstrate that initiators have functions other than positioning elements for the basal transcription complex. Rather, initiators can have a direct role in regulating the expression of specific genes. The gain or loss of initiator activity can be an important determinant of cell phenotypes.
View details for Web of Science ID 000166784800039
View details for PubMedID 11069899
T cell homeostasis and autoreactivity in rheumatoid arthritis.
Current directions in autoimmunity
2001; 3: 112-132
View details for PubMedID 11791462
Lymphoid microstructures in rheumatoid synovitis.
Current directions in autoimmunity
2001; 3: 168-187
View details for PubMedID 11791464
CD4+,CD28-T cells in rheumatoid arthritis patients combine features of the innate and adaptive immune systems
ARTHRITIS AND RHEUMATISM
2001; 44 (1): 13-20
To determine whether CD4+,CD28- T cells, which are expanded in patients with rheumatoid arthritis (RA), express receptors that typically regulate the function of natural killer (NK) cells.Expression of the NK cell surface molecules CD158, p70, CD94, CD161, and CD8alpha on T cell subsets was determined by multicolor flow cytometric analysis of peripheral blood mononuclear cells from 36 RA patients. Expression of CD161 on tissue-infiltrating CD4 T cells was determined by 2-color immunohistochemistry analysis of synovial tissue samples.Killer cell-inhibitory receptors (KIR) and killer cell-activating receptors (KAR) were exclusively expressed on CD4+,CD28- T cells, with the CD158b molecule being the most frequently detected isoform. A coordinated mechanism inducing KIR/KAR expression was suggested by similarities in the expression of CD158b on CD4 and CD8 T cells. CD4+,CD28- T cells were also positive for CD8-alphaalpha homodimers, another characteristic shared with NK cells. Of the C-type lectin NK cell receptors (NK receptors), CD94 was consistently absent, but CD161 was found on a CD4 T cell population that is significantly expanded in RA patients (P = 0.01). Involvement in disease of NK receptor-expressing CD4 T cells was suggested by the presence of CD4+,CD161+ T cells in follicular microstructures typical of rheumatoid synovitis.Patients with RA have an expanded and unusual subset of CD4 T cells that infiltrates the tissue lesions and is characterized by a deficiency of CD28, the expression of CD8-alphaalpha homodimers, and the expression of several types of HLA class I-recognizing NK receptors. CD4 T cells bearing NK receptors can bridge functions of the innate and adaptive immune systems, such as responsiveness to specific antigen, rapid release of interferon-gamma, cytotoxicity, independence from classic costimulatory pathways, and integration of multiple activating and inhibitory signals to control effector functions.
View details for Web of Science ID 000166659100003
View details for PubMedID 11212151
Clonality and longevity of CD4(+)CD28(null) T cells are associated with defects in apoptotic pathways
JOURNAL OF IMMUNOLOGY
2000; 165 (11): 6301-6307
CD4(+)CD28(null) T cells are oligoclonal lymphocytes rarely found in healthy individuals younger than 40 yr, but are found in high frequencies in elderly individuals and in patients with chronic inflammatory diseases. Contrary to paradigm, they are functionally active and persist over many years. Such clonogenic potential and longevity suggest altered responses to apoptosis-inducing signals. In this study, we show that CD4(+)CD28(null) T cells are protected from undergoing activation-induced cell death. Whereas CD28(+) T cells underwent Fas-mediated apoptosis upon cross-linking of CD3, CD28(null) T cells were highly resistant. CD28(null) T cells were found to progress through the cell cycle, and cells at all stages of the cell cycle were resistant to apoptosis, unlike their CD28(+) counterparts. Neither the activation-induced up-regulation of the IL-2R alpha-chain (CD25) nor the addition of exogenous IL-2 renders them susceptible to Fas-mediated apoptosis. These properties of CD28(null) T cells were related to high levels of Fas-associated death domain-like IL-1-converting enzyme-like inhibitory protein, an inhibitor of Fas signaling that is normally degraded in T cells following activation in the presence of IL-2. Consistent with previous data showing protection of CD28(null) cells from spontaneous cell death, the present studies unequivocally show dysregulation of apoptotic pathways in CD4(+)CD28(null) T cells that favor their clonal outgrowth and maintenance in vivo.
View details for Web of Science ID 000165467100036
View details for PubMedID 11086066
Pathogenic principles in giant cell arteritis
ELSEVIER IRELAND LTD. 2000: S9-S15
In giant cell arteritis, an immune insult in the vascular wall initiates a reaction in the artery that leads to structural changes, intimal hyperplasia, and luminal occlusion. The mechanisms triggering the immune stimulation are unknown; however, the process is strictly dependent on T cells that are found in the vicinity of the vasa vasorum in the adventitia and that produce interferon-gamma. The major effector cells in the artery are macrophages and giant cells that are ultimately under T-cell control but assume different functions depending on their location in the arterial wall. The response of the artery to the injury is maladaptive and includes mobilization and proliferation of smooth muscle cells in conjunction with matrix production and neoangionesis, resulting in the formation of a lumen-obstructive neointima. Heterogeneity in the immune insult and the resulting arterial response patterns correlate with variations in clinical disease.
View details for Web of Science ID 000089537800002
View details for PubMedID 10980331
T cell homeostasis in patients with rheumatoid arthritis
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2000; 97 (16): 9203-?
The immune system is equipped with an extremely large spectrum of structurally diverse receptors to recognize all potential antigens. This fundamental principle of receptor diversity is no longer upheld in patients with rheumatoid arthritis (RA), who have a marked contraction of the T cell receptor repertoire. In this study, the ability of RA patients to produce T cells and to maintain T cell homeostasis was examined. CD4 T cells containing T cell receptor rearrangement excision circles (TREC) were substantially reduced in RA patients; TREC levels in young adult patients matched those of controls 20 years older. Increased self-replication of T cells in RA was indicated by age-inappropriate erosion of telomeres in circulating T cells with almost complete attrition of telomeric reserves in patients 20-30 yr of age. The degree of telomere loss was not related to disease duration or the use of disease-modifying medication and was most pronounced in CD4(+)CD45RO(null) (naive) T cells. The loss of TREC-positive T cells could be a consequence of a primary defect in peripheral T cell homeostasis. Alternatively, RA patients may have impaired thymic function with the increased turnover of peripheral T cells being a secondary compensatory event.
View details for Web of Science ID 000088608000080
View details for PubMedID 10922071
Killer cell activating receptors function as costimulatory molecules on CD4(+)CD28(null) T cells clonally expanded in rheumatoid arthritis
JOURNAL OF IMMUNOLOGY
2000; 165 (2): 1138-1145
Expansion of CD4+CD28null T cells is a characteristic finding in patients with rheumatoid arthritis. Despite lacking CD28 molecules, these unusual CD4 T cells undergo clonal proliferation and form large and long-lived clonal populations. They produce high levels of IFN-gamma, exhibit autoreactivity, and have cytolytic function. The mechanisms facilitating the expansion and longevity of CD4+CD28null T cell clones in vivo are unknown. Here, we report that CD4+CD28null, but not CD4+CD28+, T cells express MHC class I-recognizing receptors normally found on NK cells. CD4+CD28null T cells preferentially expressed killer cell activating receptors (KAR), often in the absence of killer cell inhibitory receptors. Cross-linking of KAR molecules enhanced the proliferative response to TCR-mediated stimulation, but not the cytolytic function of CD4+CD28null T cells, suggesting different signaling pathways in CD4 T cells and NK cells. Triggering of KAR signaling led to the phosphorylation of several cellular targets, although the pattern of phosphorylation differed from that induced by the TCR. Aberrant expression of KAR molecules in the absence of inhibitory receptors and in the appropriate HLA setting may lead to the clonal outgrowth of autoreactive CD4+CD28null T cells commonly seen in rheumatoid arthritis.
View details for Web of Science ID 000088085600064
View details for PubMedID 10878393
Monoclonal T-cell proliferation and plaque instability in acute coronary syndromes
2000; 101 (25): 2883-2888
Unstable angina (UA) is associated with systemic inflammation and with expansion of interferon-gamma-producing T lymphocytes. The cause of T-cell activation and the precise role of activated T cells in plaque instability are not understood.Peripheral blood T cells from 34 patients with stable angina and 34 patients with UA were compared for the distribution of functional T-cell subsets by flow cytometric analysis. Clonality within the T-cell compartment was identified by T-cell receptor spectrotyping and subsequent sequencing. Tissue-infiltrating T cells were examined in extracts from coronary arteries containing stable or unstable plaque. The subset of CD4(+)CD28(null) T cells was expanded in patients with UA and infrequent in patients with stable angina (median frequencies: 10.8% versus 1.5%, P<0.001). CD4(+)CD28(null) T cells included a large monoclonal population, with 59 clonotypes isolated from 20 UA patients. T-cell clonotypes from different UA patients used antigen receptors with similar sequences. T-cell receptor sequences derived from monoclonal T-cell populations were detected in the culprit but not in the nonculprit lesion of a patient with fatal myocardial infarction.UA is associated with the emergence of monoclonal T-cell populations, analogous to monoclonal gammopathy of unknown significance. Shared T-cell receptor sequences in clonotypes of different patients implicate chronic stimulation by a common antigen, for example, persistent infection. The unstable plaque but not the stable plaque is invaded by clonally expanded T cells, suggesting a direct involvement of these lymphocytes in plaque disruption.
View details for Web of Science ID 000087810100011
View details for PubMedID 10869258
New insights into the pathogenesis of rheumatoid arthritis
OXFORD UNIV PRESS. 2000: 3-8
T lymphocytes play a critical role in the inflammatory process of rheumatoid arthritis (RA). Studies in a new animal model of RA, created by implanting human inflamed synovium into SCID mice, have confirmed that the production of matrix-degrading enzymes and pro-inflammatory cytokines is ultimately under T-cell control. T-cell dysfunction in RA patients also alters T-cell dynamics, resulting in profound abnormalities in T-cell pool composition. The cause and consequences of altered T-cell dynamics in RA are not yet understood, but factors determining T-cell homeostasis include the generation of new T cells, loss of T cells during immune responses and self-renewal of T cells within the system. Understanding the mechanisms that govern the formation of the T-cell pool in RA emphasizes the dynamic and quantitative aspects of lymphocyte behaviour in RA and has profound therapeutic implications when devising strategies to counteract T-cell dysfunction.
View details for Web of Science ID 000087832200002
View details for PubMedID 11001373
[Clinical and genetic heterogeneity of rheumatoid arthritis].
Post?py higieny i medycyny doswiadczalnej
2000; 54 (6): 845-853
The diagnostic category of rheumatoid arthritis, a syndrome of chronic inflammatory disease of the synovial membrane and of extraarticular tissues, covers a broad spectrum of clinical phenotypes. Here we propose that distinct combinations of disease risk genes produce heterogeneity of rheumatoid disease. Recognition of this genetic and clinical heterogeneity has immediate implications as it provides the opportunity to develop selective therapies for the different variants of disease.
View details for PubMedID 11227380
Cell-cell interactions in synovitis - Interactions between T cells and B cells in rheumatoid arthritis
2000; 2 (6): 457-463
In rheumatoid arthritis, T cells and B cells participate in the immune responses evolving in the synovial lesions. Interaction between T cells and B cells is probably antigen specific because complex microstructures typical of secondary lymphoid organs are generated. Differences between patients in forming follicles with germinal centers, T-cell-B-cell aggregates without germinal center reactions, or loosely organized T-cell-B-cell infiltrates might reflect the presence of different antigens or a heterogeneity in host response patterns to immune injury. Tertiary lymphoid microstructures in the rheumatoid lesions can enhance the sensitivity of antigen recognition, optimize the collaboration of immunoregulatory and effector cells, and support the interaction between the tissue site and the aberrant immune response. The molecular basis of lymphoid organogenesis studied in gene-targeted mice will provide clues to why the synovium is a preferred site for tertiary lymphoid tissue. B cells have a critical role in lymphoid organogenesis. Their contribution to synovial inflammation extends beyond antibody secretion and includes the activation and regulation of effector T cells.
View details for Web of Science ID 000167432900007
View details for PubMedID 11094459
The role of T cells in rheumatoid arthritis.
Archivum immunologiae et therapiae experimentalis
2000; 48 (5): 429-435
In rheumatoid arthritis (RA), T cells infiltrate into the synovial membrane where they initiate and maintain activation of macrophages and synovial fibroblasts, transforming them into tissue-destructive effector cells. The diversity of the disease process and the formation of complex lymphoid microstructures indicate that multiple T cell activation pathways are involved. This model is supported by the association of distinct disease patterns with different variants and combinations of HLA class II molecules. T cell pathology in RA, however, is not limited to the joint. Affected patients have major abnormalities in the T cell pool, with a marked contraction in T cell receptor diversity and an outgrowth of large clonal populations. Clonally expanded CD4+ T cells lose expression of the CD28 molecule and gain expression of perforin and granzyme. Consequently, the functional profile of expanded CD4(+)CD28null T cells is fundamentally changed and is shifted towards tissue-injurious capabilities. CD4(+)CD28null T cells are particularly important in patients with extra-articular manifestations of RA, where they may have a direct role in vascular injury. Understanding the mechanisms underlying the loss of T cell diversity and the emergence of pro-inflammatory CD4(+)CD28null T cell clonotypes may have implications for other autoimmune syndromes.
View details for PubMedID 11140470
Association of MHC and rheumatoid arthritis HLA polymorphisms in phenotypic variants of rheumatoid arthritis
2000; 2 (3): 212-216
Genes in the human leukocyte antigen (HLA) region remain the most powerful disease risk genes in rheumatoid arthritis (RA). Several allelic variants of HLA-DRB1 genes have been associated with RA, supporting a role for T-cell receptor-HLA-antigen interactions in the pathologic process. Disease-associated HLA-DRB1 alleles are similar but not identical and certain allelic variants are preferentially enriched in patient populations with defined clinical characteristics. Also, a gene dosing effect of HLA-DRB1 alleles has been suggested by the accumulation of patients with two RA-associated alleles, especially in patient subsets with a severe disease course. Therefore, polymorphisms in HLA genes are being explored as tools to dissect the clinical heterogeneity of the rheumatoid syndrome. Besides HLA polymorphisms, other risk genes will be helpful in defining genotypic profiles correlating with disease phenotypes. One such phenotype is the type of synovial lesion generated by the patient. HLA genes in conjunction with other genetic determinants may predispose patients to a certain pathway of synovial inflammation. Also, patients may or may not develop extraarticular manifestations, which are critical in determining morbidity and mortality. HLA genes, complemented by other RA risk genes, are likely involved in shaping the T-cell repertoire, including the emergence of an unusual T-cell population characterized by the potential of vascular injury, such as seen in extraarticular RA.
View details for Web of Science ID 000167357700010
View details for PubMedID 11094432
IL-16 as an anti-inflammatory cytokine in rheumatoid synovitis
JOURNAL OF IMMUNOLOGY
1999; 162 (7): 4293-4299
T lymphocytes are a major component of the inflammatory infiltrate in rheumatoid synovitis, but their exact role in the disease process is not understood. Functional activities of synovial T cells were examined by adoptive transfer experiments in human synovium-SCID mouse chimeras. Adoptive transfer of tissue-derived autologous CD8+ T cells induced a marked reduction in the activity of lesional T cells and macrophages. Injection of CD8+, but not CD4+, T cells decreased the production of tissue IFN-gamma, IL-1beta, and TNF-alpha by >90%. The down-regulatory effect of adoptively transferred CD8+ T cells was not associated with depletion of synovial CD3+ T cells or synovial CD68+ macrophages, and it could be blocked by Abs against IL-16, a CD8+ T cell-derived cytokine. In the synovial tissue, CD8+ T cells were the major source of IL-16, a natural ligand of the CD4 molecule that can anergize CD4-expressing cells. The anti-inflammatory activity of IL-16 in rheumatoid synovitis was confirmed by treating synovium-SCID mouse chimeras with IL-16. Therapy for 14 days with recombinant human IL-16 significantly inhibited the production of IFN-gamma, IL-1beta, and TNF-alpha in the synovium. We propose that tissue-infiltrating CD8+ T cells in rheumatoid synovitis have anti-inflammatory activity that is at least partially mediated by the release of IL-16. Spontaneous production of IL-16 in synovial lesions impairs the functional activity of CD4+ T cells but is insufficient to completely abrogate their stimulation. Supplemental therapy with IL-16 may be a novel and effective treatment for rheumatoid arthritis.
View details for Web of Science ID 000079278000075
View details for PubMedID 10201961
Heterogeneity of rheumatoid arthritis: from phenotypes to genotypes
SPRINGER SEMINARS IN IMMUNOPATHOLOGY
1998; 20 (1-2): 5-22
Rheumatoid arthritis (RA) is now recognized as a multigene disorder with a number of genetic polymorphisms contributing to disease pathogenesis. Here, we propose that the diagnostic category of RA includes multiple subtypes of disease and that the different phenotypes of RA correlate to different genotypes. Support for this concept has come from a reappraisal of the clinical heterogeneity of RA and the observation that HLA-DRB1 polymorphisms are useful in describing genetic heterogeneity of RA phenotypes. A series of HLA-DRB1 genes has been identified as RA associated, and in recent years emphasis has been put on the sequence similarities of these alleles. An alternative view focuses on the amino acid variations found in RA-associated HLA-DRB1 alleles with different alleles being enriched in distinct subtypes of RA. Rheumatoid factor-positive destructive joint disease is predominantly associated with the HLA-DRB1*0401 allele, while HLA-DRB1*0404 and B1*0101 predispose for milder and often seronegative disease. Expression of disease-associated alleles on both haplotypes carries a high risk for extra-articular manifestations. In particular, patients homozygous for HLA-DRB1*0401 frequently develop rheumatoid vasculities on follow-up. Besides HLA gene polymorphisms, abnormalities in the generation and function of CD4 T cells and in inflammatory pathways established in synovial lesions can be used to dissect patient subsets with different variants of RA. Emergence of CD28-deficient CD4 T cells identifies RA patients with extra-articular manifestations. These cells undergo clonal expansion in vivo, produce high amounts of IFN-gamma, and exhibit autoreactivity. Concordance of monozygotic twins for the expression of CD4+ CD28- T cells suggests a role for genetic factors in the generation of these unusual T cells. Evidence for heterogeneity of the synovial component of RA comes from studies describing three distinct patterns of lymphoid organization in the synovium. Based upon the topography of tissue-infiltrating mononuclear cells, diffuse, follicular, and granulomatous variants of rheumatoid synovitis can be distinguished. Each pattern of lymphoid organization correlates with a unique profile of tissue cytokines, demonstrating that several pathways of immune deviation modulate disease expression in RA. A dissection of RA variants would have major implications on how the disease is studied, treated, and managed. Identifying combinations of RA risk genes that correlate with disease variants could, therefore, become an important diagnostic tool.
View details for Web of Science ID 000077027100003
View details for PubMedID 9836366
Tissue cytokine patterns distinguish variants of rheumatoid synovitis
AMERICAN JOURNAL OF PATHOLOGY
1997; 151 (5): 1311-1319
Rheumatoid arthritis (RA) is a chronic inflammatory disease with primary manifestations in the synovial membrane. Tissue infiltrates are composed of T cells, B cells, and macrophages, but histopathological appearances vary widely and are rarely pathognomonic. Mechanisms underlying the phenotypic heterogeneity of rheumatoid synovitis are not known. To explore whether a correlation exists between the microscopic patterns of rheumatoid synovitis and in situ production of cytokines, tissue samples from 21 consecutive patients with clinically active RA were examined. Based upon the organization of the lymphocyte infiltrate, the synovial biopsies were categorized into three distinct subsets. Ten samples were characterized by diffuse lymphoid infiltrates without further microarrangement. In seven samples, lymphoid follicles with germinal center formation were detected, and in four specimens, granuloma formation was identified. In all specimens, cytokine transcription of interferon (IFN)-gamma, interleukin (IL)-4, IL-1 beta, tumor necrosis factor (TNF)-alpha, IL-10, and transforming growth factor-beta 1 was semiquantified with polymerase chain reaction and liquid phase hybridization. Each of the morphologically defined variants of synovitis displayed a unique cytokine profile. Low-level transcription of IFN-gamma, IL-4, IL-1 beta, and TNF-alpha was typical of diffuse synovitis. In follicular synovitis, IFN-gamma was the dominant cytokine, IL-4 was virtually undetectable, and IL-10 was abundant. Granulomatous synovitis demonstrated high transcription of IFN-gamma, IL-4, IL-1 beta, and TNF-alpha and could be clearly distinguished from the other phenotypes. To investigate whether differences in the synovial lesions were related to host factors, patients were compared for clinical parameters. Diffuse synovitis was seen in most of the patients with seronegative RA, the mildest form of the disease. In contrast, extra-articular spreading of RA with nodule formation was typically associated with granulomatous synovitis. In summary, RA patients display reproducible patterns in the organization and activity of synovial infiltrates. The correlation of microanatomy with tissue cytokine production suggests that several pathomechanisms can modulate the expression of the immune response in the synovial membrane.
View details for Web of Science ID A1997YD87800018
View details for PubMedID 9358757
TRIGGERING OF LYMPHOCYTES-T VIA EITHER T3-TI OR T11 SURFACE-STRUCTURES OPENS A VOLTAGE-INSENSITIVE PLASMA-MEMBRANE CALCIUM-PERMEABLE CHANNEL - REQUIREMENT FOR INTERLEUKIN-2 GENE-FUNCTION
JOURNAL OF BIOLOGICAL CHEMISTRY
1989; 264 (2): 1068-1076
Stimulation of human T-lymphocytes via either the surface T3-Ti antigen-major histocompatibility complex receptor complex or the T11 molecule results in clonal proliferation through a calcium-dependent mechanism. To investigate this signal transduction, plasma membrane calcium-permeable channels were characterized in T-lymphocytes by means of whole cell or single channel patch-clamp recordings. Stimulation of T-lymphocytes via either structure results in opening of an identical set of voltage-insensitive plasma membrane Ca2+-permeable channels through the action of a diffusible second messenger. Previous work with excised inside-out patches suggests that inositol 1,4,5-trisphosphate is the activating second messenger of the voltage-insensitive T-cell Ca2+-permeable channel. Since there is a significant increase in phosphoinositide turnover after stimulation via either the T3-Ti or T11 pathway, it is suggested that triggering of either structure opens a common set of channels through this mechanism. Furthermore, currents flowing through Ca2+-permeable channels are apparently autoregulated, as inward conductance is abolished by elevation of Ca2+ concentration in the bathing solution. In particular, the steady-state rise in interleukin-2 (T-cell growth factor) mRNA is dependent on the rise of [Ca2+]i resulting from ion movement across this channel.
View details for Web of Science ID A1989R820000062
View details for PubMedID 2562953