Objective:To study the effect of adoptive transfer of regulatory T cells(Tregs)on the repair phase of ischemia/reperfusion(IR)induced renal injury in mice. Methods:A total of 24 C57BL/6 mice aged 6-week-old were divided into Sham group,IR group,high-dose transfer group(HT),and low-dose transfer group(LT). Approximately 5 × 106 and 1 × 105 Tregs were injected intravenously into mice by tail vein 1 d before IR injury induced. Left renal pedicle was bluntly dissected and clamped with a microvascular clamp for 45 min and reperfusion 4 d to establish IR renal injury model. Left renal pedicle was only separated without clipping in the Sham group. HE staining was performed to evaluate morphology changes of renal tissues. Immunohistochemical and flow cytometry were performed to detect the infiltrating of Tregs(CD4+CD25+);the expression changes of Ki67,tumor necrosis factor-α(TNF-α),IL-16 and IL-10 were determined by immunohistochemistry,Western blotting and/or ELISA. Results:Compared to the IR group and the LT group,the damage of renal pathological was reduced,cell proliferation,the infiltration of Tregs and the expression of IL-10 were significantly increased(P < 0.05),and the expression of TNF-α and IL-6 were decreased(P < 0.05)in the HT group. Conclusion:Adoptive transfer of Tregs had a dose-dependent protective effect on renal ischemia-reperfusion-induced injury,which is possibly related to inhibition of the proinflammatory cytokines TNF-α,IL-6 and increase of anti-inflammatory cytokine IL-10.