The Preliminary Study On The Induction Of Immunetolerance Function By Exosomes Derived From Dendritic Cells

Dendritic cells (DCs) are unique professional major antigen presenting cells (APCs) capable of stimulating naive T cells in the primary immune response. Immature DCs (iDCs) can induce peripheral tolerance, while mature DCs (mDCs) can stimulate T cells activation. DCs can secrete small membrane vesicles called exosomes which are 30-100 nm diameter called Dex, expressing some function associated molecules of DCs, such as MHC class I, MHC class II molecules and costimulatory molecules B7 and adhesive molecules CD54 and so on. The function of Dex depends on their original cell types and status.To investigate the roles of Dex derived from DCs in the induction of T cells immunetolerance and study the feasibility of reducing allotransplantation rejection by donor Dex in vitro, iDCs were induced from human peripheral blood mononuclear cells, mDCs were treated by LPS. Then the phenotype of iDCs and mDCs was assayed by flow cytometry; IDex from iDCs and mDex from mDCs were isolated by ultracentrifugation and ultrafiltration; The biological function of allogeneic iDex and mDex in allogeneic mixed lymphocyte reaction (MLR) as allotransplantation rejection model in vitro was analyzed by Cell Counting Kit-8.The results showed allogeneic mDex might stimulate the proliferation of allogeneic T cells when mDCs presented, however ,iDex might suppress the proliferation of allogeneic T cells when iDCs presented in MLR. Therefor mDex derived from mDCs can induce immunity response of T cells and have great prospect in antitumor therapy; Just the opposite iDex derived from iDCs may maintain peripheral tolerance and play important roles in allotransplantation tolerance. So it will be a novel way in prevention allotransplantation rejection and in treating autoimmune disease.Meanwhile, to investigate the molecular mechanisms of Dex derived from regulatory DCs induced immunetolerance and to provide a theory base on anti-tumour immune responses and prevention allotransplantation rejection, we induced regulatory DCs (rDCs) by treating iDCs with TGF-β1 and IL-10, the phenotype of rDCs and normal DCs (nDCs) and the capacity of phagocytizing of them were assayed by flow cytometry. Then the capacity of secreting Dex was compared by Bradford; The function associated molecules of rDex and iDex were detected by Western blotting; The effect of inhibiting MLR by allogeneic rDex and iDex and the capacity of immunetolerance induced by rDex and iDex were analyzed by Cell Counting Kit-8. As a result, it was demonstrated that TGF-β1 and IL-10 might down-regulate the expressions of costimulatory molecules, including CD80, CD83 and CD86 and induced regulatory DCs to secrete more rDex than iDCs; Moreover the suppression of rDex was significantly stronger than iDex and rDex might express more FasL, leading to a more potent suppression of MLR. It is evident that rDex secreted by rDCs induced with TGF-β1 and IL-10 can play important roles in immune tolerance. It has the potential application in prevention allotransplantation rejection in the future.