Tfr Cells Restrain Rejection of Kidney Allografts by Limiting Pro-Inflammatory Cytokines in B cells [scRNA-seq]
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ABSTRACT: Pathogenic antibodies produced by alloreactive B cells mediate antibody-mediated rejection (ABMR) after kidney transplantation, but the mechanisms controlling these antibodies remain poorly understood. Follicular Regulatory T (Tfr) cells modulate follicular helper T (Tfh) cell-mediated B cell responses but their roles in controlling alloreactive antibody are unknown. Here, we studied the developmental signals and functions of Tfr cells in allogeneic kidney transplantation. We show that costimulatory blockade alters the development of Tfr cells disproportionately by decreasing germinal center (GC)-like Tfr cells and increasing follicular-like Tfr cells. Functionally, Tfr cell deletion resulted in accelerated rejection and increases in donor-specific B cells in both draining lymph nodes and kidney allografts. Mechanistically, Tfr cell deletion increased GC B cell expression of pro-inflammatory cytokines such as IL-15. Neutralization of IL-15 compensated for the loss of Tfr cells and prolonged kidney transplant recipient survival. Together these data demonstrate the signals for Tfr cell development and how these cells restrain rejection by limiting alloreactive B cell responses.
Project description:Assessment of transcriptional programs of germinal center B cells isolated from lymph nodes of Tfr-depleted (Tfr-DTR) and control (Tfr-Con) recipients post-transplantation to investigate the role of Tfr cells in kidney transplant rejection.
Project description:T follicular helper (TFH) cells promote affinity maturation of B cells in germinal centers (GCs), whereas T follicular regulatory (TFR) cells limit GC reaction. Store-operated Ca2+ entry (SOCE) through Ca2+ release-activated Ca2+ (CRAC) channels mediated by STIM and ORAI proteins is a fundamental signaling pathway in T lymphocytes. Here we show that SOCE is required for the differentiation and function of both TFH and TFR cells. Conditional deletion of Stim1 and Stim2 genes in T cells or Treg cells results in spontaneous autoantibody production and humoral autoimmunity. Conversely, antibody-mediated immune responses following viral infection critically depend on SOCE in TFH cells. Mechanistically, STIM1 and STIM2 control early TFR and TFH cell differentiation through NFAT-mediated IRF4, BATF and Bcl-6 expression. SOCE plays a dual role in GC response by controlling TFH and TFR cell function, thus enabling protective B cell responses and preventing humoral autoimmunity. RNAseq analyses of WT and Stim1Stim2 DKO follicular T cells and non-follicular T cells; 4-6 mice per cohort in duplicates. Mice were infected for 10 days with LCMV.
Project description:T follicular regulatory (TFR) cells are found in the germinal center (GC) response and help shape the antibody (Ab) response. Whether TFR cells have a suppressive role, a helper role or both types of roles in the GC is unclear. Here, we addressed TFR cell function using 3 different strains of TFR cell mutant mice. After immunization, GC B cells but not T follicular helper (TFH) cell positively correlated with TFR cell levels. Using a gene profiling approach, we found that TFH cells from TFR-deficient mice showed strong up-regulation of granzyme B (Gzmb) and other effector CD8 T cell genes, many of which were Stat4 dependent. This aberrant cytotoxic T cell gene profile was increased in TFR-deficient mice crossed on a pro-inflammatory background. We detected Gzmb+ and Eomesodermin+ TFH cells and a higher rate of apoptotic GC B cells in the absence of TFR cells. Klrg1+ TFH cells expressed higher Gzmb and less IL-4 and IL-21. Our data show that TFR cells repress the development of abnormal cytotoxic TFH cells that correlate with a lower GC and Ab response. This data shows a novel mode of helper function for TFR cells in the GC response.
Project description:T follicular helper cells (TFH) are critical for the development and maintenance of germinal centers (GC) and humoral immune responses. During chronic HIV/SIV infection TFH accumulate, possibly as a result of antigen persistence. The HIV/SIV-associated TFH expansion may also reflect lack of regulation by suppressive follicular regulatory CD4+ T-cells (TFR). TFR are natural regulatory T-cells (TREG) that migrate into the follicle and, similarly to TFH, up-regulate CXCR5, Bcl-6, and PD1. Here we identified TFR as CD4+CD25+FoxP3+CXCR5+PD1hiBcl-6+ within lymph nodes of rhesus macaques (RM) and confirmed their localization within the GC by immunohistochemistry. RNA sequencing showed that TFR exhibit a distinct transcriptional profile with shared features of both TFH and TREG, including intermediate expression of FoxP3, Bcl-6, PRDM1, IL-10, and IL-21. In healthy, SIV-uninfected RM, we observed a negative correlation between frequencies of TFR and both TFH and GC B-cells as well as levels of CD4+ T-cell proliferation. Following SIV infection, the TFR/TFH ratio was reduced with no change in the frequency of TREG or TFR within the total CD4+ T-cell pool. Finally, we examined whether higher levels of direct virus infection of TFR were responsible for their relative depletion post-SIV infection. We found that TFH, TFR and TREG sorted from SIV- infected RM harbor comparable levels of cell-associated viral DNA. Our data suggests that TFR may contribute to the regulation and proliferation of TFH and GC B-cells in vivo and that a decreased TFR/TFH ratio in chronic SIV infection may lead to unchecked expansion of both TFH and GC B-cells. TFR, TFH, TREG and bulk CD4 cells were sorted from spleens of 5 uninfected and 5 infected RM.
Project description:The extent to which tissue-resident memory T (TRM) cells in transplanted organs possess alloreactivity is uncertain. This study investigates the alloreactive potential of TRM cells in kidney explants from four patients who experienced severe acute rejection leading to graft loss. Alloreactive T-cell receptors (TCRs) clones were identified in pre-transplant blood samples through mixed lymphocyte reactions, followed by single-cell RNA and TCR sequencing of the proliferated recipient T cells. Subsequently, these TCR clones were traced in the TRM cells of kidney explants, which were also subjected to single-cell RNA and TCR sequencing. The proportion of TRM cells expressing an alloreactive TCR in the four kidney explants varied from 0% to 9%. Notably, these alloreactive TCRs were predominantly found among CD4+ and CD8+ TRM cells with an effector phenotype. Intriguingly, alloreactive clones were present not only in recipient-derived TRM cells but also in donor-derived TRM cells, constituting up to 4% of the donor population, suggesting the presence of self-reactive TRM cells. Overall, our study demonstrates that T cells with alloreactive potential present in the peripheral blood prior to transplantation can infiltrate the kidney transplant and adopt a TRM phenotype.
Project description:Kidney transplant recipients are at particular risk for developing tumors, many of which are now routinely treated with immune checkpoint inhibitors (ICIs); however, ICI therapy can precipitate transplant rejection. We utilized TCR sequencing to identify and track alloreactive T cells in a patient with melanoma who experienced kidney transplant rejection following ICI therapy. ICI therapy was associated with a sharp increase in circulating alloreactive CD8+ T cell clones, many of which were also detected in the rejected kidney but not at tumor sites. Longitudinal and cross-tissue TCR analyses revealed unintended expansion of alloreactive CD8+ T cells induced by ICI therapy for cancer, coinciding with ICI-associated organ rejection.
Project description:Kidney transplant recipients are at particular risk for developing tumors, many of which are now routinely treated with immune checkpoint inhibitors (ICIs); however, ICI therapy can precipitate transplant rejection. We utilized TCR sequencing to identify and track alloreactive T cells in a patient with melanoma who experienced kidney transplant rejection following ICI therapy. ICI therapy was associated with a sharp increase in circulating alloreactive CD8+ T cell clones, many of which were also detected in the rejected kidney but not at tumor sites. Longitudinal and cross-tissue TCR analyses revealed unintended expansion of alloreactive CD8+ T cells induced by ICI therapy for cancer, coinciding with ICI-associated organ rejection.
Project description:Kidney transplant recipients are at particular risk for developing tumors, many of which are now routinely treated with immune checkpoint inhibitors (ICIs); however, ICI therapy can precipitate transplant rejection. We utilized TCR sequencing to identify and track alloreactive T cells in a patient with melanoma who experienced kidney transplant rejection following ICI therapy. ICI therapy was associated with a sharp increase in circulating alloreactive CD8+ T cell clones, many of which were also detected in the rejected kidney but not at tumor sites. Longitudinal and cross-tissue TCR analyses revealed unintended expansion of alloreactive CD8+ T cells induced by ICI therapy for cancer, coinciding with ICI-associated organ rejection.
Project description:Antibody-mediated rejection, caused by antibodies against the donor human leukocyte antigen (HLA) molecules plays a fundamental role in graft rejection in transplantation. Most significant is transplant patients who generate antibodies against the donor HLA-DQ have the highest risk of rejection. In this study, we investigated the role of indirect CD4 T cell epitopes in the formation of donor-specific antibodies (DSA). Using antigen mapping techniques in kidney and heart transplant recipients with HLA-DQ DSA, we identified two polymorphic hotspots in the HLA-DQ gene that generated alloreactive CD4 T cell responses. To study the functional significance of indirect CD4 T cells, we first mapped epitopes recognised by H2-Kb C57Bl6 mice against a skin graft from H2-Kd Balb/c mice. We identified a CD4 T cell epitope, specific for amino acids 287-301 derived from the H2-Kd protein, that generated tetramer-binding Kd287+ CD4 T cells during rejection. Importantly, the transfer of Kd287+ CD4 T cells into T cell-deficient mice was sufficient to drive an antibody response against the donor H2-Kd molecule. Lastly, we found that administration of systemic high-dose donor H2-Kd peptides combined with CTLA4-Ig reduced the formation of Kd287+ CD4 T cells and diminished DSA formation. Together, these findings demonstrate that the identification of donor antigens indicates the potential for inducing donor-specific immune tolerance in transplantation.
Project description:Tolerance of mouse kidney allografts arises in grafts that develop regulatory Tertiary Lymphoid Organs (rTLOs). scRNAseq data and adoptive transfer of alloreactive T cells post-transplant showed that cytotoxic CD8+ T cells are reprogrammed within the accepted graft to an exhausted/regulatory-like phenotype. Establishment of rTLOs was required since adoptive transfer of alloreactive T cells prior to transplantation results in kidney allograft rejection. Despite intragraft CD8+ cells with a regulatory phenotype, they were not essential for the induction and maintenance of kidney allograft tolerance. Analysis of scRNAseq data from allograft kidneys and malignant tumors identified similar regulatory-like cell types within the T cell clusters. Induction of cytotoxic CD8+ T cell dysfunction of infiltrating cells appears to be a beneficial mechanistic pathway that protects the kidney allotransplant from rejection through a process we call “defensive tolerance.” This pathway has implications for our understanding of allotransplant tolerance and tumor resistance to host immunity.