Study On The Effect And Mechanism Of Toll-like Receptor 9 And Myeloid-derived Suppressive Cells On Decidual Regulatory T Cell

Objective:Normal pregnancy is considered as semi-allograft.There are complex immune response and immune regulation between fetal and mother so that maternal-fetal immune tolerance was established instead of rejection.Once the maternal-fetal lose balance,it lead to gestational disease,such as abortion.It has been demonstrated that regulatory T cells(Treg)play an important role in maternal-fetal immune tolerance.In unexplained Recurrent spontaneous abortion(URSA),Treg cells show deficiet number and function.However,it is not clear why Treg cells are deficit in URSA.Previous studies showed Toll like receptor 9(TLR9)and Myeloid-derived suppressive cells(MDSCs)are involved in the process.Under the specific pregnant microenviroment,Are Treg cells were regulated by TLR9 or MDSCs cells?If it is possible,what is its mechanism?There has not been any reports.Method and Design:Animal experiments were performed and the deciduas from URSA patients and normal pregnant women were collected.Flowcytometry,Western blot,Realtime PCR,Immunohistochemitry,ELISA,MACS and immunofluorescence were used.We detect the effects of excessive TLR9 on the pattern of decidual immune cells and cytokines in abortion mice,investigate the direct effect of TLR9 activation on the apoptosis of Treg cells and its mechanism and observe the indirect effect of TLR9 signaling on the apoptosis of Treg cells through macrophage and its mechanism;In addition,we analyze the association between decidual MDSCs and URSA,explore the mechanism of MDSCs recruitment to the human deciduas and investigate the regulation of G-MDSCs on Treg cells in diciduas and its mechanisms.Results:Excessive TLR9 signaling contributed to URSA via an effect on Treg cells apoptosis by activation of Caspase 8/3.We have identified a mechanism by which TNF-?from TLR9 activated–macrophage promotes Tregs apoptosis in abortion mice.Also,we found that MDSCs cells participate in the maternal fetal immune tolerance as a new cell subsets in deciduas.CXCR2 promotes G-MDSCs recruitment and facilitates Arginase I expression and activity of these cells at maternal-fetal interface.G-MDSCs had an important role in regulation of Treg cells.The effects of G-MDSCs on Treg depend on cell-to-cell contact.G-MDSCs promote Foxp3 induction from CD4~+CD25~-T cells depending on the membrane-bound TGF-?.The regulation of TGF-?on?-catenin translocation was sufficient for G-MDSCs induced-Foxp3expression.Conclusion:Decidual excessive TLR9 signaling and deficit G-MDSCs may lead to the decrease in the number of decidal Treg cells in URSA patients.The results not only provide new theoretical evidence for the pathogenesis of URSA,but also provide experimental evidence for the prevention of URSA by interfering with the excessive expression of TLR9 or/and the induction of G-MDSCs cells.