All Publications

  • High-resolution phenotyping of early acute rejection reveals a conserved alloimmune signature. Cell reports Harden, J. T., Wang, X. n., Toh, J. n., Sang, A. X., Brown, R. A., Esquivel, C. O., Martinez, O. M., Krams, S. M. 2021; 34 (9): 108806


    Alloimmune responses in acute rejection are complex, involving multiple interacting cell types and pathways. Deep profiling of these cell types has been limited by technology that lacks the capacity to resolve this high dimensionality. Single-cell mass cytometry is used to characterize the alloimmune response in early acute rejection, measuring 37 parameters simultaneously, across multiple time points in two models: a murine cardiac and vascularized composite allotransplant (VCA). Semi-supervised hierarchical clustering is used to group related cell types defined by combinatorial expression of surface and intracellular proteins, along with markers of effector function and activation. This expression profile is mapped to visualize changes in antigen composition across cell types, revealing phenotypic signatures in alloimmune T cells, natural killer (NK) cells, and myeloid subsets that are conserved and that firmly distinguish rejecting from non-rejecting grafts. These data provide a comprehensive, high-dimensional profile of cellular rejection after allograft transplantation.

    View details for DOI 10.1016/j.celrep.2021.108806

    View details for PubMedID 33657374

  • Establishment of Heterotopic Hind Limb Transplantation Model in the Mouse. Transplantation proceedings Wang, X. n., Harden, J. T., Sang, A. X., Esquivel, C. O., Martinez, O. n., Krams, S. M. 2020


    The mouse is the most widely used animal for establishing in vivo models in transplant research. However, because of the advanced microsurgical skills required for these operations, the vascularized composite transplantation model in mouse has proven to be technically challenging. The purpose of this report is to describe novel modifications in surgical techniques to establish a consistent and reliable mouse model of hind limb transplantation.Forty C57BL/6 male mice, half as donors and half as recipients, were used in this study. The donor hind limb was harvested and transplanted into the recipient's ipsilateral cervical region by anastomosing the donor femoral artery to the recipient common carotid artery with a modified sleeve technique. The donor femoral vein was mounted with a modified cuff and inserted into the recipient external jugular vein. The graft was evaluated at 2 weeks postoperatively.The modified cuff and modified sleeve technique facilitated anastomoses. The time spent on either of the donor operation and recipient operation was about 45 minutes. The graft survival rate was 80% (16 of 20) at 2 weeks after transplant. There was minimal blood loss and no infections were noted.Revised surgical techniques using a modified cuff proved to be a safe, reliable, and reproducible strategy in establishing a mouse model of hind limb heterotopic transplantation. The consistent graft survival in this syngeneic study demonstrates that this model can serve as a useful tool for further studies in vascularized composite transplantation.

    View details for DOI 10.1016/j.transproceed.2020.10.039

    View details for PubMedID 33341263

  • Natural killer cells as modulators of alloimmune responses CURRENT OPINION IN ORGAN TRANSPLANTATION Mbiribindi, B., Harden, J. T., Pena, J. K., Krams, S. M. 2019; 24 (1): 37–41
  • Application of Mass Cytometry for Analysis of the Alloimmune Response in a Model of Vascularized Composite Allotransplantation Harden, J. T., Sang, A. X., Qu, X., Esquivel, C., Martinez, O. M., Krams, S. M. LIPPINCOTT WILLIAMS & WILKINS. 2018: S198
  • Micro-RNAs in transplant tolerance CURRENT OPINION IN ORGAN TRANSPLANTATION Harden, J. T., Krams, S. M. 2018; 23 (1): 66–72


    Micro-RNAs (miRNAs) are highly conserved small RNA molecules that have selective gene-regulatory functions. This posttranscriptional regulation by miRNAs is critical for many immunological processes. Many developments in establishing the biological role of miRNAs in solid organ transplantation have been generated in the last decade. Discoveries of immune regulation by miRNAs, resulting in graft prolongation and transplant tolerance, are rapidly advancing and are the subject of this review.Many elegant experimental studies have revealed intriguing associations between transplant tolerance and specific miRNA profiles. These findings have provided insight into the miRNAs critical for sustaining immune suppression, and have revealed common miRNA pathways that should be further investigated and/or targeted therapeutically. Further reports have strategized and corroborated different methods of manipulating miRNA expression for prolonging allograft survival, yielding promising preclinical evidence of the efficacy of miRNA-based therapies.The review covers these recent developments in miRNA research that can revolutionize how we implement diagnostics and prognostics and how we can strategize transplantation therapies.

    View details for PubMedID 29064833

  • Natural killer cells as modulators of alloimmune responses. Current opinion in organ transplantation Mbiribindi, B. n., Harden, J. T., Pena, J. K., Krams, S. M. 2018


    Natural killer (NK) cells are effector cells of the innate immune system that can lyse target cells without prior sensitization and are important in host defense to virally infected and transformed cells. Although the concept of 'missing-self' would suggest NK cells could target foreign allografts, the prevailing dogma has been that NK cells are not active participants in the rejection of solid organ allografts. This review summarizes recent studies that challenge this conclusion and instead suggest NK cells are important in outcomes posttransplant.NK cells expressing specific cell surface receptors may promote graft damage and rejection. However, recent studies suggest some NK cell subsets have tolerogenic or immunoregulatory potential and promote graft stability, suggesting a dichotomous role for NK cells after transplant. Furthermore, NK cells respond to cells infected with cytomegalovirus and Epstein-Barr virus, and studies suggest some NK cells have immune memory.Our understanding of the role of NK cells posttransplant has evolved from 'no role' to the current idea that NK cells may have 'complex interactions' that impact graft outcomes. Additional studies, using cutting edge techniques to comprehensively analyze the phenotypic and functional subsets of NK cells in transplant recipients, are clearly necessary.

    View details for PubMedID 30480641