Clinical significance of myeloid-derived suppressor cells in human renal transplantation with acute T cell-mediated rejection.

Myeloid-derived suppressor cells (MDSCs) are negative regulators of the immune response and are in part responsible for the inhibition of the T cell-mediated immune response. A recent paper indicated that MDSCs were involved in prolonged allograft survival in animal models of transplantation, but the significance of MDSCs in human renal transplantation is still unknown. In our study, 50 patients with biopsy-proven acute T cell-mediated rejection (ATCMR) were included. The ratio of MDSCs in peripheral blood mononuclear cell (PBMC) was evaluated with FACS, and the patients were divided into the MDSCs high group (MDSCs, >10 %) or the MDSCs low group (MDSCs, <10 %). We compared the allograft function, severity of tissue injury, and long-time survival between the two groups. In the MDSCs high group, allograft function was significantly increased compared with the MDSCs low group. Furthermore, we found that isolated MDSCs from transplant recipients are capable of expanding regulatory T cell (Treg), meanwhile, inhibiting production of IL-17 in vitro. We also found that the ratio between Foxp3(+) and IL-17-producing CD4(+) T cells positively correlated with MDSCs frequency in PBMC. In conclusion, we demonstrated a potential role for MDSCs in prolonging allograft survival after ATCMR, and this was associated with higher CD4(+)Foxp3(+)/CD4(+)IL-17(+) ratio in PBMC.