Abstract: Maternal-fetal interface of the immune tolerance is essential to maintain normal pregnancy. Toll like
receptor2（TLR2）and TLR4 are one of the important innate immune receptor molecules. TLR2 can recognize peptidoglycan, TLR4 can recognize lipopolysaccharide. Through the signal transduction mechanism, such as caused by NF-κB transcription factor activation and regulation of cytokines TNF-α, IFN-γ and IL-12 etc. A growing evidences show that these cytokines with unexplained recurrent spontaneous abortion（URSA） are closely related to Th1/Th2 cytokine imbalance. This paper discusses the possible role of the expression of TLR2 and TLR4 in the placenta, as well as in URSA in summary.

Key words: Abortion, Chorionic villi, Decidua, Toll-like receptor 2, Toll-like receptor 4