Differential Role of B Cells and IL-17 Versus IFN-γ During Early and Late Rejection of Pig Islet Xenografts in Mice

Abstract

Background Xenogeneic islet transplantation is an emerging therapeutic option for diabetic patients. However, immunological tolerance to xenogeneic islets remains a challenge. Methods The current study used a pig-to-mouse discordant xenogeneic islet transplant model to examine anti-donor xenogeneic immune responses during early and late rejection, and to determine experimental therapeutic interventions that promote durable pig islet xenograft survival. Results We found that during early acute rejection of pig islet xenografts, the rejecting hosts exhibited a heavy graft infiltration with B220+ B cells and a robust anti-pig antibody production. In addition, early donor-stimulated IL-17 production, but not IFN-γ production, dominated during early acute rejection. Recipient treatment with donor apoptotic 1-ethyl-3-(3′-dimethylaminopropyl)-carbodiimide-treated splenocytes (ECDI-SP) significantly inhibited anti-donor IL-17 response, and when combined with B cell depletion and a short course of rapamycin led to survival of pig islet xenografts beyond 100 days in ~65% recipients. Interestingly, treated recipients in this model experienced late rejection between 100 – 200 days posttransplant, which coincided with B cell reconstitution and an ensuing emergence of a robust anti-donor IFN-γ, but not IL-17, response. Conclusions These findings reveal that early and late rejection of pig islet xenografts may be dominated by different immune responses, and that maintenance of long-term xenogeneic tolerance will require strategies that target the temporal sequence of anti-xenogeneic immune responses.

Rejection of xenogeneic porcine islets in humanized mice is characterized by graft-infiltrating Th17 cells and activated B cells

“…This combinatorial regimen, composed of donor ECDI‐SP, B cell depletion with rituximab, and a short course of rapamycin, shows promising efficacy for promoting porcine islet xenograft survival for up to 60 days after transplantation. Although donor ECDI‐SP has been shown to induce durable tolerance in allogeneic murine islet transplantation, it alone is ineffective in tolerance induction for xenogeneic islet transplantation: B cell depletion is additionally required for long‐term xenograft survival which can be further augmented by transient administration of rapamycin . However, B cell depletion and rapamycin given in the absence of donor ECDI‐SP provided only a modest survival benefit to porcine islet xenografts in this model, indicating the critical contribution by donor ECDI‐SP for long‐term tolerance.…”

“…Published data suggest that early rejection of xenogeneic islets in a pig‐to‐B6 mouse model may be mediated by a predominant anti‐donor T cell IL‐17 response in contrast to a predominant anti‐donor T cell IFN‐γ response observed during rejection of allogeneic islets. We next examined the contributing human T cell cytokine responses in xenogeneic rejection of porcine islets by HuMice.…”

“…In this study, we conducted pig‐to‐humanized mouse islet transplantation experiments with or without an investigational tolerance therapy. Our approach for tolerance draws from our previous experience in a pig‐to‐mouse islet transplantation model, in which peritransplant recipient treatment with a combination of (1) ethyl carbodiimide‐fixed donor splenocytes (ECDI‐SPs), (2) rituximab, and (3) rapamycin is highly effective in protecting porcine islets in C57BL/6(B6) recipients. Here, we aimed to apply this regimen, collectively termed as “triple therapy,” to our HuMice model and report its efficacy, mechanisms of graft protection, and potential clinical application for xenotransplantation.…”

NK cell and Th17 responses are differentially induced in murine cytomegalovirus infected renal allografts and vary according to recipient virus dose and strain

“…Th17 cells responding to MCMV peptides occur in immunocompetent mice after acute MCMV infection (52). IL-17 is expressed during clinical renal allograft rejection and in animal models for renal, islet xenograft, and cardiac transplant rejection, but CMV was not evaluated in these models (53–59). Liver transplant patients with CMV antigenemia/DNAemia had greater IL-17 mRNA expression in peripheral blood both at baseline and over time compared to patients without CMV infection (60).…”

Harnessing Apoptotic Cells for Transplantation Tolerance: Current Status and Future Perspectives

“…Our lab has serendipitously discovered that donor splencoytes simply treated with a chemical cross-linker called ethylene carbodiimide (ECDI) undergo rapid and efficient early apoptosis [18*]. When infused intravenously, they are readily phagocytized by recipients’ splenic antigen-presenting cells (APCs) [19], and induce robust donor-specific tolerance in murine models of allogeneic and xenogeneic transplantation [18*, 19–24]. This approach is currently being tested in non-human primate models of allogeneic and xenogeneic pancreatic islet transplantations with promising results (Hering, Miller and Luo, unpublished data).…”