CD4~+Nrp1~+Regulatory T Cells Induce The Renal Protect Effect Of Ischemic Preconditioning

Objective: Ischemic reperfusion is one of the most important causes of acute kidneyinjury. The T cell mediated inflammatory had been proved to be the major mechanismof kidney ischemic reperfusion injury (IRI). A short-time preconditioning ischemiaspurs kidney tolerance to following ischemic dysfunction. And the underlyingmechanisms of ischemic preconditioning (IP) are thought to involve adaptive changeswithin the injured tissue. Because regulatory T cells play a key role in inflammatorysuppressing and tolerance maintenance, we hypothesized that CD4~+Nrp1~+regulatoryT cells induce the protect effect of ischemic preconditioning in kidney.Methods: To confirm this, C57BL/6mice underwent25min of bilateral renalclamping or sham operation.7days after operation, a second bilateral renal clamping(35min) was performed to the mice. The renal pathology and serum creatinine weredetermined. At7days after IP (or sham operation), purified CD4~+T or CD8~+T fromspleen were adoptively transferred into wild type C57mice. After transfusion, thesemice underwent35min of renal IRI. The proportion of CD4~+Nrp1~+regulatory T cellswas detected by flow cytometry. CD4~+Nrp1~+regulatory T cells were isolated from IPmice to demonstrate the immunosuppressive effect in vitro. Meanwhile, we depletionof regulatory T cells by anti-CD25monoclonal antibody, and to reveal the effect ofCD4~+Nrp1~+regulatory T cells in renal protection. Results：The mice in IP/IRI group underwent mild renal damage compared to mice inSham/IRI group, determined by pathology and creatinine tested. The mice receivingCD4~+T from IP mice had significantly reduced serum creatinine compared with micereceiving other type of T lymphocytes.7days after operation, the proportion of CD4~+Nrp1~+regulatory T cells was4-folder higher in IP group than in sham operation group.In vitro analysis the CD4~+Nrp1~+T cells isolated from IP mice, the Foxp3expressingrate was above95%in kidney, spleen and periphery blood. CD4~+Nrp1~+regulatory Tcells suppressed lymphocytes proliferation in vitro. Depletion of regulatory T cells byanti-CD25monoclonal antibody deprived the adoptive protect effect of IP.Conclusion: These results demonstrated that immune cells primed after renal IRIwith an increasing proportion of CD4~+Nrp1~+regulatory T cells and therebysuppressed the inflammatory and injury during a second episode of IRI.