Adoptive Transfer With In Vitro Expanded Human Regulatory T Cells Protects Against Porcine Islet Xenograft Rejection via Interleukin-10 in

T cell-mediated rejection remains a barrier to the clinical ap-plication of islet xenotransplantation. Regulatory T cells (Treg) regulate immune responses by suppressing effector T cells. This study aimed to determine the ability of human Treg to prevent islet xenograft rejection and the mechanism(s) involved. Neo-natal porcine islet transplanted NOD-SCID IL2rg2/2 mice re-ceived human peripheral blood mononuclear cells (PBMC) with in vitro-expanded autologous Treg in the absence or presence of anti-human interleukin-10 (IL-10) monoclonal antibody. In addi-tion, human PBMC-reconstituted recipient mice received recom-binant human IL-10 (rhIL-10). Adoptive transfer with expanded autologous Treg prevented islet xenograft rejection in human PBMC-reconstituted mice by inhibiting graft infiltration of effector cells and their function. Neutralization of human IL-10 shortened xenograft survival in mice receiving human PBMC and Treg. I