Academic Appointments

All Publications

  • CMV-Responsive CD4 T Cells Have a Stable Cytotoxic Phenotype Over the First Year Post-Transplant in Patients Without Evidence of CMV Viremia. Frontiers in immunology Higdon, L. E., Ahmad, A. A., Schaffert, S., Margulies, K. B., Maltzman, J. S. 2022; 13: 904705


    Cytomegalovirus (CMV) infection is a known cause of morbidity and mortality in solid organ transplant recipients. While primary infection is controlled by a healthy immune system, CMV is never eradicated due to viral latency and periodic reactivation. Transplantation and associated therapies hinder immune surveillance of CMV. CD4 T cells are an important part of control of CMV reactivation. We therefore investigated how CMV impacts differentiation, functionality, and expansion of protective CD4 T cells from recipients of heart or kidney transplant in the first year post-transplant without evidence of CMV viremia. We analyzed longitudinal peripheral blood samples by flow cytometry and targeted single cell RNA sequencing coupled to T cell receptor (TCR) sequencing. At the time of transplant, CD4 T cells from CMV seropositive transplant recipients had a higher degree of immune aging than the seronegative recipients. The phenotype of CD4 T cells was stable over time. CMV-responsive CD4 T cells in our transplant cohort included a large proportion with cytotoxic potential. We used sequence analysis of TCRalphabeta to identify clonal expansion and found that clonally expanded CMV-responsive CD4 T cells were of a predominantly aged cytotoxic phenotype. Overall, our analyses suggest that the CD4 response to CMV is dominated by cytotoxicity and not impacted by transplantation in the first year. Our findings indicate that CMV-responsive CD4 T cells are homeostatically stable in the first year after transplantation and identify subpopulations relevant to study the role of this CD4 T cell population in post-transplant health.

    View details for DOI 10.3389/fimmu.2022.904705

    View details for PubMedID 35837398

  • Functional Consequences of Memory Inflation after Solid Organ Transplantation. Journal of immunology (Baltimore, Md. : 1950) Higdon, L. E., Schaffert, S., Cohen, R. H., Montez-Rath, M. E., Lucia, M., Saligrama, N., Margulies, K. B., Martinez, O. M., Tan, J. C., Davis, M. M., Khatri, P., Maltzman, J. S. 2021


    CMV is a major infectious complication following solid organ transplantation. Reactivation of CMV leads to memory inflation, a process in which CD8 T cells expand over time. Memory inflation is associated with specific changes in T cell function, including increased oligoclonality, decreased cytokine production, and terminal differentiation. To address whether memory inflation during the first year after transplantation in human subjects alters T cell differentiation and function, we employed single-cell-matched TCRalphabeta and targeted gene expression sequencing. Expanded T cell clones exhibited a terminally differentiated, immunosenescent, and polyfunctional phenotype whereas rare clones were less differentiated. Clonal expansion occurring between pre- and 3 mo posttransplant was accompanied by enhancement of polyfunctionality. In contrast, polyfunctionality and differentiation state were largely maintained between 3 and 12 mo posttransplant. Highly expanded clones had a higher degree of polyfunctionality than rare clones. Thus, CMV-responsive CD8 T cells differentiated during the pre- to posttransplant period then maintained their differentiation state and functional capacity despite posttransplant clonal expansion.

    View details for DOI 10.4049/jimmunol.2100405

    View details for PubMedID 34551963

  • Evolution of Cytomegalovirus-Responsive T Cell Clonality following Solid Organ Transplantation. Journal of immunology (Baltimore, Md. : 1950) Higdon, L. E., Schaffert, S., Huang, H., Montez-Rath, M. E., Lucia, M., Jha, A., Saligrama, N., Margulies, K. B., Martinez, O. M., Davis, M. M., Khatri, P., Maltzman, J. S. 2021


    CMV infection is a significant complication after solid organ transplantation. We used single cell TCR alphabeta sequencing to determine how memory inflation impacts clonality and diversity of the CMV-responsive CD8 and CD4 T cell repertoire in the first year after transplantation in human subjects. We observed CD8 T cell inflation but no changes in clonal diversity, indicating homeostatic stability in clones. In contrast, the CD4 repertoire was diverse and stable over time, with no evidence of CMV-responsive CD4 T cell expansion. We identified shared CDR3 TCR motifs among patients but no public CMV-specific TCRs. Temporal changes in clonality in response to transplantation and in the absence of detectable viral reactivation suggest changes in the repertoire immediately after transplantation followed by an expansion with stable clonal competition that may mediate protection.

    View details for DOI 10.4049/jimmunol.2100404

    View details for PubMedID 34551964

  • Association of Premature Immune Aging and Cytomegalovirus After Solid Organ Transplant FRONTIERS IN IMMUNOLOGY Higdon, L. E., Gustafson, C. E., Ji, X., Sahoo, M. K., Pinsky, B. A., Margulies, K. B., Maecker, H. T., Goronzy, J., Maltzman, J. S. 2021; 12
  • Association of Premature Immune Aging and Cytomegalovirus After Solid Organ Transplant. Frontiers in immunology Higdon, L. E., Gustafson, C. E., Ji, X., Sahoo, M. K., Pinsky, B. A., Margulies, K. B., Maecker, H. T., Goronzy, J., Maltzman, J. S. 2021; 12: 661551


    Immune function is altered with increasing age. Infection with cytomegalovirus (CMV) accelerates age-related immunological changes resulting in expanded oligoclonal memory CD8 T cell populations with impaired proliferation, signaling, and cytokine production. As a consequence, elderly CMV seropositive (CMV+) individuals have increased mortality and impaired responses to other infections in comparison to seronegative (CMV-) individuals of the same age. CMV is also a significant complication after organ transplantation, and recent studies have shown that CMV-associated expansion of memory T cells is accelerated after transplantation. Thus, we investigated whether immune aging is accelerated post-transplant, using a combination of telomere length, flow cytometry phenotyping, and single cell RNA sequencing. Telomere length decreased slightly in the first year after transplantation in a subset of both CMV+ and CMV- recipients with a strong concordance between CD57+ cells and short telomeres. Phenotypically aged cells increased post-transplant specifically in CMV+ recipients, and clonally expanded T cells were enriched for terminally differentiated cells post-transplant. Overall, these findings demonstrate a pattern of accelerated aging of the CD8 T cell compartment in CMV+ transplant recipients.

    View details for DOI 10.3389/fimmu.2021.661551

    View details for PubMedID 34122420

    View details for PubMedCentralID PMC8190404

  • Transplantation and CMV promote premature aging of CD8 T cells Higdon, L. E., Gustafson, C. E., Ji, X., Maecker, H. T., Maltzman, J. S. AMER ASSOC IMMUNOLOGISTS. 2021
  • Sestrins teach old T cells new tricks. Science immunology Maltzman, J. S. 2020; 5 (47)


    Sestrin proteins dampen TCR signaling and induce antigen-independent natural killer-like cytotoxicity in highly differentiated CD8 T cells.

    View details for DOI 10.1126/sciimmunol.abc4460

    View details for PubMedID 32358171

  • To debug or not to debug, a question worth asking. Science immunology Higdon, L. E., Maltzman, J. S. 2019; 4 (41)


    Recipient antibiotic pre-treatment protects both mice and humans from ischemia-reperfusion injury after liver transplantation.

    View details for DOI 10.1126/sciimmunol.aaz9474

    View details for PubMedID 33681670

    View details for PubMedCentralID PMC7932049

  • To debug or not to debug, a question worth asking. Science immunology Higdon, L. E., Maltzman, J. S. 2019; 4 (41)


    Recipient antibiotic pretreatment protects both mice and humans from ischemia-reperfusion injury after liver transplantation.

    View details for DOI 10.1126/sciimmunol.aaz9474

    View details for PubMedID 31676498

  • Transplantation Alters Function and Clonality of Cytomegalovirus-Responsive T Cells Higdon, L. E., Schaffert, S., Saligrama, N., Davis, M. M., Khatri, P., Maltzman, J. S. LIPPINCOTT WILLIAMS & WILKINS. 2019
  • Single cell immune profiling in transplantation research AMERICAN JOURNAL OF TRANSPLANTATION Higdon, L. E., Schaffert, S., Khatri, P., Maltzman, J. S. 2019; 19 (5): 1278–87

    View details for DOI 10.1111/ajt.15316

    View details for Web of Science ID 000471342300007

  • Optimization of single-cell plate sorting for high throughput sequencing applications JOURNAL OF IMMUNOLOGICAL METHODS Higdon, L. E., Cain, C. J., Colden, M. A., Maltzman, J. S. 2019; 466: 17–23
  • The outstanding questions in transplantation: It's about time... AMERICAN JOURNAL OF TRANSPLANTATION Azzi, J., Raimondi, G., Mas, V., Riella, L. V., Elfadawy, N., Safa, K., Wojciechowski, D., Kanak, M., Nog, R., Maltzman, J. S., Ford, M. L., Pober, J. S., Luo, X., Rothstein, D., Miller, M. L., Matthews, D., Burlingham, W., Levings, M., Heeger, P., Higdon, L., Gill, J., Gill, R. G., Alegre, M. 2018; 18 (1): 271–72

    View details for PubMedID 28758364

  • Expanding the Toolkit for the Study of Allospecific B and T Cell Responses TRANSPLANTATION Higdon, L. E., Maltzman, J. S. 2017; 101 (11): 2661–62

    View details for PubMedID 29059129

    View details for PubMedCentralID PMC5724565

  • T cells expand after solid organ transplantation in the absence of CMV disease. American journal of transplantation Higdon, L. E., Trofe-Clark, J., Liu, S., Margulies, K. B., Sahoo, M. K., Blumberg, E., Pinsky, B. A., Maltzman, J. S. 2017


    Cytomegalovirus (CMV) is a major cause of morbidity and mortality in solid-organ transplant recipients. Approximately 60% of adults are CMV seropositive indicating previous exposure. Following resolution of primary infection, CMV remains in a latent state. Reactivation is controlled by memory T cells in healthy individuals; transplant recipients have reduced memory T cell function due to chronic immunosuppressive therapies. In this study, CD8(+) T cell responses to CMV polypeptides IE-1 and pp65 were analyzed in sixteen CMV seropositive renal and cardiac transplant recipients longitudinally pre- and post-transplant. All patients received standard of care maintenance immunosuppression, antiviral prophylaxis and CMV viral load monitoring, with approximately half receiving T cell depleting induction therapy. The frequency of CMV-responsive CD8(+) T cells, defined by production of effector molecules in response to CMV peptides, increased during the course of a year post-transplant. The increase commenced after the completion of antiviral prophylaxis, and these T cells tended to be terminally differentiated effector cells. Based on this small cohort, these data suggest that even in the absence of disease, antigenic exposure may continually shape the CMV-responsive T cell population post-transplant. This article is protected by copyright. All rights reserved.

    View details for DOI 10.1111/ajt.14227

    View details for PubMedID 28199780

  • Virtual Global Transplant Laboratory Standard Operating Procedures for Blood Collection, PBMC Isolation, and Storage. Transplantation direct Higdon, L. E., Lee, K., Tang, Q., Maltzman, J. S. 2016; 2 (9)


    Research on human immune responses frequently involves the use of peripheral blood mononuclear cells (PBMC) immediately, or at significantly delayed timepoints, after collection. This requires PBMC isolation from whole blood and cryopreservation for some applications. It is important to standardize protocols for blood collection, PBMC isolation, cryopreservation, and thawing that maximize survival and functionality of PBMC at the time of analysis. This resource includes detailed protocols describing blood collection tubes, isolation of PBMC using a density gradient, cryopreservation of PBMC, and thawing of cells as well as preparation for functional assays. For each protocol, we include important considerations, such as timing, storage temperatures, and freezing rate. In addition, we provide alternatives so that researchers can make informed decisions in determining the optimal protocol for their application.

    View details for PubMedID 27795993

  • Caught Off Center: Rethinking the Requirements for Antibody Affinity Maturation IMMUNITY Higdon, L. E., Cancro, M. P. 2015; 43 (1): 5-6


    Antibody affinity maturation involves selective survival of high affinity B cells and is thought to require the germinal center (GC) microenvironment. In this issue of Immunity, Di Niro et al. (2015) challenge this view, showing that low affinity B cells initiate Salmonella responses and affinity mature outside of GCs.

    View details for DOI 10.1016/j.immuni.2015.07.002

    View details for Web of Science ID 000360101100003

    View details for PubMedID 26200006

  • ICOS and Bcl6-dependent pathways maintain a CD4 T cell population with memory-like properties during tuberculosis JOURNAL OF EXPERIMENTAL MEDICINE Moguche, A. O., Shafiani, S., Clemons, C., Larson, R. P., Dinh, C., Higdon, L. E., Cambier, C. J., Sissons, J. R., Gallegos, A. M., Fink, P. J., Urdahl, K. B. 2015; 212 (5): 715-728


    Immune control of persistent infection with Mycobacterium tuberculosis (Mtb) requires a sustained pathogen-specific CD4 T cell response; however, the molecular pathways governing the generation and maintenance of Mtb protective CD4 T cells are poorly understood. Using MHCII tetramers, we show that Mtb-specific CD4 T cells are subject to ongoing antigenic stimulation. Despite this chronic stimulation, a subset of PD-1(+) cells is maintained within the lung parenchyma during tuberculosis (TB). When transferred into uninfected animals, these cells persist, mount a robust recall response, and provide superior protection to Mtb rechallenge when compared to terminally differentiated Th1 cells that reside preferentially in the lung-associated vasculature. The PD-1(+) cells share features with memory CD4 T cells in that their generation and maintenance requires intrinsic Bcl6 and intrinsic ICOS expression. Thus, the molecular pathways required to maintain Mtb-specific CD4 T cells during ongoing infection are similar to those that maintain memory CD4 T cells in scenarios of antigen deprivation. These results suggest that vaccination strategies targeting the ICOS and Bcl6 pathways in CD4 T cells may provide new avenues to prevent TB.

    View details for DOI 10.1084/jem.20141518

    View details for Web of Science ID 000353898100013

    View details for PubMedID 25918344

  • Receptor revision in CD4 T cells is influenced by follicular helper T cell formation and germinal-center interactions PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Higdon, L. E., Deets, K. A., Friesen, T. J., Sze, K., Fink, P. J. 2014; 111 (15): 5652-5657


    Peripheral CD4 T cells in Vβ5 transgenic (Tg) C57BL/6J mice undergo tolerance to an endogenous superantigen encoded by mouse mammary tumor virus 8 (Mtv-8) by either deletion or T-cell receptor (TCR) revision. Revision is a process by which surface expression of the Vβ5(+) TCR is down-regulated in response to Mtv-8 and recombination activating genes are expressed to drive rearrangement of the endogenous TCRβ locus, effecting cell rescue through the expression of a newly generated, non-self-reactive TCR. In an effort to identify the microenvironment in which revision takes place, we show here that the proportion of T follicular helper cells (Tfh) and production of high-affinity antibody during a primary response are increased in Vβ5 Tg mice in an Mtv-8-dependent manner. Revising T cells have a Tfh-like surface phenotype and transcription factor profile, with elevated expression of B-cell leukemia/lymphoma 6 (Bcl-6), CXC chemokine receptor 5, programmed death-1, and other Tfh-associated markers. Efficient revision requires Bcl-6 and is inhibited by B lymphocyte-induced maturation protein-1. Revision completes less efficiently in the absence of signaling lymphocytic activation molecule-associated protein although initiation proceeds normally. These data indicate that Tfh formation is required for the initiation of revision and germinal-center interactions for its completion. The germinal center is known to provide a confined space in which B-cell antigen receptors undergo selection. Our data extend the impact of this selective microenvironment into the arena of T cells, suggesting that this fluid structure also provides a regulatory environment in which TCR revision can safely take place.

    View details for DOI 10.1073/pnas.1321803111

    View details for Web of Science ID 000334288600054

    View details for PubMedID 24706795

  • Recent thymic emigrants are preferentially incorporated only into the depleted T-cell pool PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Houston, E. G., Higdon, L. E., Fink, P. J. 2011; 108 (13): 5366-5371


    Recent thymic emigrants (RTEs) are the youngest subset of peripheral T cells, and they differ functionally and phenotypically from the rest of the naïve T-cell pool. RTEs are present in the peripheral T-cell pool throughout life but are the most common subset of T cells in neonates and adults recovering from lymphoablation. Using a murine model to study the homeostasis of RTEs, we show that under lymphoreplete conditions, RTEs are at a competitive disadvantage to already established mature naïve (MN) T cells. This disadvantage may be caused by a defect in survival, because RTEs may transduce homeostatic signals inefficiently, and their ability to survive is enhanced with increased expression of IL-7 receptor or B-cell lymphoma 2 (Bcl-2). Conversely, under lymphopenic conditions, enhanced proliferation by RTEs allows them to out-compete their MN T-cell counterparts. These results suggest that in times of need, such as in neonates or lymphopenic adults, RTEs perform well to fill the gaps in the peripheral T-cell pool, but when the periphery already is full, many RTEs are not incorporated into the pool of recirculating lymphocytes.

    View details for DOI 10.1073/pnas.1015286108

    View details for Web of Science ID 000288894800046

    View details for PubMedID 21402911