Project description:The efficacy of costimulation blockade (CTLA4Ig/belatacept) in transplantation is reduced by an increased incidence of T cell-mediated rejection, which also persists after induction therapy with anti-thymocyte globulin (ATG). Herein, we investigate why ATG fails to prevent costimulation blockade-resistant rejection and how this barrier can be overcome. ATG did not prevent graft rejection in a murine heart transplant model of CTLA4Ig therapy and induced a pro-inflammatory cytokine environment. While ATG improved the balance between Tregs and effector T cells in the peripheral compartment, it had no such effect within cardiac allografts, which showed signs of inflammation. Neutralizing IL-6 alleviated inflammation, increased intragraft Treg frequencies long-term, and enhanced intragraft IL-10 and Th2 cytokine expression. IL-6 blockade together with ATG led to long-term, rejection-free heart graft survival under CTLA4Ig therapy. Combining ATG with IL-6 blockade prevents costimulation blockade-resistant rejection, thereby eliminating a major impediment to clinical use of costimulation blockers in transplantation.
Project description:The efficacy of costimulation blockade (CTLA4Ig/belatacept) in transplantation is reduced by an increased incidence of T cell-mediated rejection, which also persists after induction therapy with anti-thymocyte globulin (ATG). Herein, we investigate why ATG fails to prevent costimulation blockade-resistant rejection and how this barrier can be overcome. ATG did not prevent graft rejection in a murine heart transplant model of CTLA4Ig therapy and induced a pro-inflammatory cytokine environment. While ATG improved the balance between Tregs and effector T cells in the peripheral compartment, it had no such effect within cardiac allografts, which showed signs of inflammation. Neutralizing IL-6 alleviated inflammation, increased intragraft Treg frequencies long-term, and enhanced intragraft IL-10 and Th2 cytokine expression. IL-6 blockade together with ATG led to long-term, rejection-free heart graft survival under CTLA4Ig therapy. Combining ATG with IL-6 blockade prevents costimulation blockade-resistant rejection, thereby eliminating a major impediment to clinical use of costimulation blockers in transplantation.
Project description:Antithymocyte globulin (ATG) is a widely used immunosuppressive agent, yet its off-target vascular effects remain a clinical challenge in part due to a lack of relevant human models. To elucidate the effects of ATG on liver sinusoidal endothelial cells, we performed bulk RNA-seq analysis of iPSC-derived liver sinusoidal endothelial cells (iLSECs) exposed to ATG or normal rabbit IgG (rIgG) for 4 or 24 hours. We here report that ATG induces a proinflammatory program in iLSECs, characterized by upregulation of chemokines and prothrombotic factors. While minimal differences were observed at 4 hours, expression patterns clustered separately at 24 hours between rIgG- and ATG-treated cells. At 24 hours, ATG upregulated gene expressions, including chemokines such as CCL2, CXCL1, and CXCL5, as well as prothrombotic mediators SPP1 and SERPINE1, with downregulation of the vasoprotective gene NOS3. Gene set enrichment analysis identified that the gene set "Overview of Proinflammatory and Profibrotic Mediators" was significantly enriched in ATG-treated iLSECs at 24 hours compared to rIgG controls. This dataset provides critical insight to uncover the direct mode of action of ATG on LSEC beyond its immunosuppressive function.
Project description:Low-dose anti-thymocyte globulin (ATG) transiently preserves C-peptide and lowers HbA1c in individuals with recent-onset type 1 diabetes (T1D); however, the mechanisms of action and features of the response remain unclear. Here, we characterized the post hoc immunological outcomes of ATG administration and their potential use as biomarkers of metabolic response to therapy (i.e., improved preservation of endogenous insulin production).METHODSWe assessed gene and protein expression, targeted gene methylation, and cytokine concentrations in peripheral blood following treatment with ATG (n = 29), ATG plus granulocyte colony-stimulating factor (ATG/G-CSF, n = 28), or placebo (n = 31).RESULTSTreatment with low-dose ATG preserved regulatory T cells (Tregs), as measured by stable methylation of FOXP3 Treg-specific demethylation region (TSDR) and increased proportions of CD4+FOXP3+ Tregs (P < 0.001) identified by flow cytometry. While treatment effects were consistent across participants, not all maintained C-peptide. Responders exhibited a transient rise in IL-6, IP-10, and TNF-α (P < 0.05 for all) 2 weeks after treatment and a durable CD4+ exhaustion phenotype (increased PD-1+KLRG1+CD57- on CD4+ T cells [P = 0.011] and PD1+CD4+ Temra MFI [P < 0.001] at 12 weeks, following ATG and ATG/G-CSF, respectively). ATG nonresponders displayed higher proportions of senescent T cells (at baseline and after treatment) and increased methylation of EOMES (i.e., less expression of this exhaustion marker).CONCLUSIONAltogether in these exploratory analyses, Th1 inflammation-associated serum and CD4+ exhaustion transcript and cellular phenotyping profiles may be useful for identifying signatures of clinical response to ATG in T1D.TRIAL REGISTRATIONClinicalTrials.gov NCT02215200.FUNDINGThe Leona M. and Harry B. Helmsley Charitable Trust (2019PG-T1D011), the NIH (R01 DK106191 Supplement, K08 DK128628), NIH TrialNet (U01 DK085461), and the NIH NIAID (P01 AI042288).
Project description:Background Immune tolerance and persistent mixed chimerism can be achieved reproducibly after combined organ and hematopoietic cell transplantation in mice conditioned with total lymphoid irradiation plus anti-thymocyte globulin. We studied the safety and reproducibility of this approach in a cohort of kidney transplant patients, and tried to identify immune monitoring procedures that can predict tolerance and guide complete immunosuppressive drug withdrawal. Methods Ten patients conditioned with 10 doses of total lymphoid irradiation and 5 doses of anti-thymocyte globulin were given kidney transplants and an injection of CD34+ hematopoietic progenitor cells and T cells from HLA matched donors. Blood cell monitoring included changes in chimerism, balance of T cell subsets, gene expression, and responses to donor alloantigens. Results Nine of 10 patients developed multi-lineage chimerism without graft versus host disease (GVHD), and all had excellent graft function at the last observation point. Five of these with chimerism persisting for at least 12 months were completely withdrawn from immunosuppressive drugs for 6 to 35 months. Blood cells from patients off drugs showed development of specific unresponsiveness to donor alloantigens, “tolerance” profiles on gene microarrays, early high ratios of regulatory versus conventional naïve T cells, and early high levels of chimerism among NK cells. Conclusions Total lymphoid irradiation, and anti-thymocyte globulin promoted the development of persistent chimerism and tolerance in a cohort of patients given kidney transplants and donor cell injections. Assays were identified that can assist in the safe withdrawal of immunosuppressive drugs.
Project description:Background Immune tolerance and persistent mixed chimerism can be achieved reproducibly after combined organ and hematopoietic cell transplantation in mice conditioned with total lymphoid irradiation plus anti-thymocyte globulin. We studied the safety and reproducibility of this approach in a cohort of kidney transplant patients, and tried to identify immune monitoring procedures that can predict tolerance and guide complete immunosuppressive drug withdrawal. Methods Ten patients conditioned with 10 doses of total lymphoid irradiation and 5 doses of anti-thymocyte globulin were given kidney transplants and an injection of CD34+ hematopoietic progenitor cells and T cells from HLA matched donors. Blood cell monitoring included changes in chimerism, balance of T cell subsets, gene expression, and responses to donor alloantigens. Results Nine of 10 patients developed multi-lineage chimerism without graft versus host disease (GVHD), and all had excellent graft function at the last observation point. Five of these with chimerism persisting for at least 12 months were completely withdrawn from immunosuppressive drugs for 6 to 35 months. Blood cells from patients off drugs showed development of specific unresponsiveness to donor alloantigens, M-bM-^@M-^\toleranceM-bM-^@M-^] profiles on gene microarrays, early high ratios of regulatory versus conventional naM-CM-/ve T cells, and early high levels of chimerism among NK cells. Conclusions Total lymphoid irradiation, and anti-thymocyte globulin promoted the development of persistent chimerism and tolerance in a cohort of patients given kidney transplants and donor cell injections. Assays were identified that can assist in the safe withdrawal of immunosuppressive drugs. 45 Agilent Microarray samples were conducted, including 16 tolerance patients, 10 chronic rejection patients, 5 healthy normal controls, and 7 paired pre and post-transplant induced tolerance patients. The aim is to see whether induced tolerance patients show operational tolerance gene expression signature and can withdraw or minimize the immunosuppression regimens.
Project description:We aimed to investigate the effect of increased cold ischemia time (CIT) on gene expression profiles of implantation and clinically indicated biopsies early after transplantation and the impact of basiliximab (BAS) versus rabbit antithymocyte globulin (rATG) induction therapies on clinical outcomes and intragraft molecular features
Project description:Despite the life-saving successes of solid organ transplantation, the number of individuals needing organ transplant far exceeds the number of organs available for use each year. Porcine xenotransplantation, or the use of pig organs for transplantation in people, holds substantial promise but xenograft rejection in humans is poorly understood. T cell rejection by the host immune system is a major challenge for human allografts and may limit the longevity of porcine xenografts. To study the xenograft rejection, we evaluated T cell responses and repertoire dynamics across tissues following porcine xenograft transplantation in a decedent model over 61 days after bilateral native kidney nephrectomy. Despite induction with anti-thymocyte globulin and ongoing immune suppression consisting of rituximab, corticosteroids, calcineurin inhibition, and proliferation inhibition, human T cell infiltration of the xenograft was observed and was associated with xenograft dysfunction. Longitudinal analysis of T cell clonotypes in biopsies of the xenokidney revealed accumulation of clonal human CD4 and CD8 T cell responses. Moreover, circulating activated T cells, including circulating T follicular helper (cTfh), were xeno-reactive and increased in frequency around rejection events. A single CD8 clonotype dominated in the circulation leading up to the acute cellular rejection event. Following re-treatment with anti-thymocyte globulin and intensification of corticosteroids, the xeno-reactive T cell clonotypes were dramatically diminished in frequency in lymph nodes, though not eliminated. Together, these data demonstrate T cell repertoire dynamics across tissues in the setting of xenograft rejection and highlight opportunities for early surveillance and potential intervention.