Objective To investigate the expression of Toll-like receptor 4 (TLR4) and CD80 in unexplained recurrent spontaneous abortion and their relationship,discuss its possible roles in guiding eugenics,and provide a new idea for clinical diagnosis and prevention.Methods The study group were 60 cases with unexplained recurrent spontaneous abortion patients.The control group included 30 cases of normal early pregnancy without previous history of adverse pregnancy.The expressions of TLR4 and CD80 were detected with immunohistochemistry in the peripheral blood,chorion,and decidua from each case.Results TLR4 had higher expression in the peripheral blood,the chorion and decidua from the recurrent spontaneous abortion women than that from normal pregnancy women (P ＜ 0.05).Levels of CD80 were significantly higher in recurrent spontaneous abortion group than in normal pregnancy group (P ＜ 0.05).There was a positive correlation between TLR4 and CD80 (r =0.982,0.986,and 0.776,P ＜0.01).Conclusions The study shows that TLR4 and CD80 were expressed in peripheral blood lymphocytes and villi and decidua of early pregnancy (normal pregnancy or abnormal pregnancy).Higher expressions of TLR4 and CD80 might play an important role in the occurrence of recurrent spontaneous abortion.