Elevated T Regulatory Cells in Long-Term Stable Transplant Tolerance in Rhesus Macaques Induced by Anti-CD3 Immunotoxin and Deoxyspergualin

Abstract

Regulatory T cells (Tregs) are implicated in immune tolerance and are variably dependent on IL-10 for in vivo function. Brief peritransplant treatment of multiple nonhuman primates (NHP) with anti-CD3 immunotoxin and deoxyspergualin has induced stable (5–10 years) rejection-free tolerance to MHC-mismatched allografts, which associated with sustained elevations in serum IL-10. In this study, we demonstrate that resting and activated PBMC from long-term tolerant NHP recipients are biased to secrete high levels of IL-10, compared with normal NHP PBMC. Although IL-10-producing CD4+ Tregs (type 1 regulatory cells (TR1)/IL-10 Tregs) were undetectable (<0.5%) in normal rhesus monkeys, 7.5 ± 1.7% of circulating CD4+ T cells of tolerant rhesus recipients expressed IL-10. In addition to this >15-fold increase in Tr1/IL-10 Tregs, the tolerant monkeys exhibited a nearly 3-fold increase in CD4+CD25+ Tregs, 8.1 ± 3.0% of CD4 T cells vs 2.8 ± 1.4% in normal cohorts (p < 0.02). The frequency of CD4+CD25+IL-10+ cells was elevated 5-fold in tolerant vs normal NHP (1.8 ± 0.9% vs 0.4 ± 0.2%). Rhesus CD4+CD25+ Tregs exhibited a memory phenotype, and expressed high levels of Foxp3 and CTLA-4 compared with CD4+CD25− T cells. Also, NHP CD4+CD25+ Tregs proliferated poorly after activation and suppressed proliferation of CD4+CD25− effector T cells, exhibiting regulatory properties similar to rodent and human CD4+CD25+ Tregs. Of note, depletion of CD4+CD25+ Tregs restored indirect pathway antidonor responses in tolerant NHP. Our study demonstrates an expanded presence of Treg populations in tolerant NHP recipients, suggesting that these adaptations may be involved in maintenance of stable tolerance.

Infusion of Stably Immature Monocyte-Derived Dendritic Cells Plus CTLA4Ig Modulates Alloimmune Reactivity in Rhesus Macaques

“…Moreover, immature human allogeneic Mo-DC have been shown to induce Treg (6). It is also of interest that increases in circulating Treg (54) or recruitment of Treg to the allograft interstitium (55) have been correlated with tolerance to renal allografts in rhesus monkeys.…”

Adoptive transfer of CD4+CD25+ regulatory cells combined with low-dose sirolimus and anti-thymocyte globulin delays acute rejection of renal allografts in Cynomolgus monkeys

“…Stable tolerance has been demonstrated to be related to high level of IL-10 and high frequencies of CD4 + CD25 bright Tregs and CD4 + IL-10 + Tr1 cells [43,44]. Our data showed the frequencies of CD4 + CD25 bright Tregs were higher in the recipients received Tregs alone or combined with sirolimus, compared with those in untreated or tacrolimus-treated monkeys, but no change of CD4 + IL-10 + Tr1 cells was found in the monkeys of all groups.…”

Immune Modulation by Regulatory T Cells in Helicobacter pylori-Associated Diseases

“…Tr1 cells are induced in vitro when antigen is presented by immature or tolerogenic DC in the presence of IL-10 [11]. In vivo, Tr1 cells are generated during IL-10 administration or with drugs preventing DC maturation [12,13]. The main suppressive function of Tr1 cells is, not surprisingly, their secretion of IL-10 and TGF following T cell receptor mediated activation by specific antigens.…”