ECDI-Fixed Donor Splenocytes Prolong Allografts Survival Via Producing M2 Macrophages Polarization And Tregs Induction

BackgroundImmune rejection is the most common complication and major limitation of allogeneic tissue transplantation.The regulatory T cells(Tregs)play a central role in inhibiting rejection and promoting allograft tolerance.A more complete understanding of Treg biology may lead to novel therapeutic approaches to enhance Treg numbers and function.1-ethyl-3-(3’-dimethylaminopropyl)-carbodiimide(ECDI)fixed splenocytes has been reported effective to induce donor-specific tolerance and evoke immunosuppression in transplant.However,the mechanism between ECDI-fixed splenocyte and Tregs remains uncertain.Alternative macrophage(M2)as the member of nonspecific immunity system,play significant roles in inducing Treg and inhibiting inflammation.ObjectiveTo explore the relationship between ECDI-SPs and the polarization of M2macrophages,and to reveal the mechanism of ECDI-SPs prolonging the survival of allograft。MethodsThe objective of this study was to determine the effectiveness of ECDI-SPs for induction of tolerance in mice allograft model.Firstly,we explored the relationship between ECDI-fixed donor splenocytes treatment and the polarization of recipient macrophages.C57BL/6 recipient mice received BALB/c donor full-thickness skin transplantation,along with the infusion of ECDI-SPs plus rapamycin prolongs the survival of skin allografts.ResultsWe found that by facilitating CREB phosphorylate,ECDI-SPs effectively induced macrophages M2 polarization,which can further lead the expansion of CD4~+Foxp3~+Tregs.Macrophage engulfed ECDI-SPs have increased the level of IL-10 and suppressed the expression of inflammatory cytokines.These findings reveal the mechanism of donor-derived ECDI-SPs extending allograft survival,which provided the theoretical basis for the further therapeutic manipulation.ConclusionECDI-fixed donor splenocytes facilitate M2 macrophages polarization via enhancing CREB phosphorylate,then M2 macrophages strengthened the secretion of IL-10 andTregs induction,leading to the prolonging of allografts survival.