Regulatory functions of self-restricted MHC class II allopeptide-specific Th2 clones in vivo

Abstract

We studied T-cell clones generated from grafts of rejecting and tolerant animals and investigated the regulatory function of Th2 clones in vitro and in vivo. To prevent allograft rejection, we treated LEW strain recipient rats of WF strain kidney grafts with CTLA4Ig to block CD28-B7 costimulation. We then isolated epitope-specific T-cell clones from the engrafted tissue, using a donor-derived immunodominant class II MHC allopeptide presented by recipient antigen-presenting cells. Acutely rejected tissue from untreated animals yielded self-restricted, allopeptide-specific T-cell clones that produced IFN-γ, whereas clones from tolerant animals produced IL-4 and IL-10. Adoptive transfer into naive recipients of Th1 clones, but not Th2 clones, induced alloantigen-specific delayed-type hypersensitivity (DTH) responses. In addition, Th2 clones suppressed DTH responses mediated by Th1 clones in vivo and blocked Th1 cell proliferation and IFN-γ production in vitro. A pilot human study showed that HLA-DR allopeptide-specific T-cell clones generated from patients with chronic rejection secrete Th1 cytokines, whereas those from patients with stable graft function produce Th2 cytokines in response to donor-specific HLA-DR allopeptides. We suggest that self-restricted alloantigen-specific Th2 clones may regulate the alloimmune responses and promote long-term allograft survival and tolerance. See related Commentary on pages 797-798rats undergoing acute vascularized allograft rejection express a restricted TCR Vβ repertoire and transfer DTH responses in vivo (16). In this study, we compared for the first time, to our knowledge, the functions of self-restricted alloreactive T-cell clones generated from grafts of rejecting and tolerant animals and analyzed the putative regulatory functions of Th2 clones in vitro and in vivo. Results of a pilot study in kidney transplant recipients with chronic rejection or stable graft function establish the biological relevance of our animal studies in humans. Our results confirm the regulatory functions of alloreactive Th2 clones and provide an invaluable tool for the study of the functions of Th1 and Th2 clones in acute/chronic allograft rejection and tolerance in vivo. MethodsAnimals. Inbred 200-250 g male Lewis (LEW; RT1 l ) rats were used as recipients and Wistar Furth (WF; RT1 u ) rats served as donors. They were purchased from Harlan Sprague-Dawley Inc. (Indianapolis, Indiana, USA).Rat kidney transplantation. LEW rats underwent bilateral nephrectomies and received heterotopic MHCincompatible WF renal allografts. For the purpose of this study, we used two groups of animals. The first group was unmodified and the rejecting graft was harvested on day 7. The second group was treated with a single injection of human cytotoxic lymphocyte activation factor 4 (CTLA4Ig; Bristol Myers Squibb Co., Princeton, New Jersey, USA) on day 2 after transplant and the graft was harvested after 100 days. This protocol of CTLA4Ig administration has previously been shown by Sayegh's group to induce long-term a...

The Role of CC Chemokine Receptor 5 (CCR5) in Islet Allograft Rejection

“…One could speculate that the Th2 switch observed in the graft and periphery of CCR5-deficient animals may be protective against islet allograft destruction. However, a regulatory function of Th2 cells in alloimmune responses remains controversial (25)(26)(27)). Animals lacking the Th2 cytokine IL-4 can accept allografts (28), although this is not a universal finding in all models (29).…”

Human endothelial cells generate Th17 and regulatory T cells under inflammatory conditions

“…immune regulation | MHC class II T he allogeneic response to organ transplantation was initially considered to be predominantly mediated by the Th1 population whereas the Th2 population was believed to oppose Th1 cell activation, thus favoring graft survival (1). Recent studies have identified additional CD4 + T cell subsets including IL-17-producing CD4 + T cells (Th17) and CD4 + FoxP3 + regulatory T cells (Tregs) (2).…”

Chronic Rejection

“…In the supernatants of these cultures, TNF-␣, IFN-␥, and IL-2 were detectable in this strain combination (LEW into WF.1L). Interestingly, in the reversed strain combination, in which no significant signs of chronic rejection were observed, IL-4 and IL-10 were detectable not only in the culture supernatants but also in the kidney grafts of those animals, reflecting type 2 cytokine expression, previously associated with transplantation tolerance (30). It has been speculated that Th2 responses may be responsible for the development of chronic rejection (31); in contrast, we found that chronic rejection was associated with a Th1 response, in keeping with human studies that have shown that alloreactive T cells cloned from chronically rejecting patients were universally of the Th1 phenotype (32).…”