Non-human primate regulatory T cells: current biology and implications for transplantation

Abstract

Regulatory T cells (Treg) offer potential for improving long-term outcomes in cell and organ transplantation. The non-human primate model is a valuable resource for addressing issues concerning the transfer of Treg therapy to the clinic. Herein, we discuss the properties of non-human primate Treg and prospects for their evaluation in allotransplantation and xenotransplantation.

FIGURE 1

(A), Issues that govern the successful application of Treg therapy in transplantation. (B–D), Highly-suppressive Treg can be expanded/induced from cynomolgus monkey blood. (B), CD4⁺CD127^loCD25⁺ (nTreg) were flow-sorted from PBMC. They were stimulated in vitro with anti-CD3/CD28-coated beads, in the presence of human IL-2 (500U/ml), with or without TGFβ1 (5ng/ml). In parallel, CD4⁺CD127^hiCD25⁻ T cells were sorted and induced to convert into regulatory cells (iTreg) by stimulation with anti-CD3/CD28-coated beads in the presence of IL-2 and TGFβ1, with or without retinoic acid (RA; 5ng/ml). The fold-expansion obtained under each condition at multiple time points is indicated. (C), Preservation of Foxp3 expression in expanded nTreg was tested by intracellular staining after 16 days of culture. (D), The suppressive capacity of expanded nTreg was tested in MLR. PBMC were obtained from the same source as nTreg and stimulated in vitro with irradiated allogeneic PBMC (1:2 responder to stimulator ratio). Titrated numbers of nTreg or nTreg (TGFβ1) were added to the cultures at the indicated Treg to responder ratios. Responder cell proliferation was quantified by thymidine incorporation on day 4. nTreg expanded with IL-2 alone did not inhibit proliferation significantly (data not shown). (E), as in D, T cells induced to convert into iTreg were tested for their suppressive capacity in MLR. p<0.02; **, p<0.05 for all comparisons indicated.