Toll-like receptors (TLRs) form the major family of pattern recognition receptors that are involved in innate immunity. Innate immune responses against microorganisms at the maternal—fetal interface may have a significant impact on the success of pregnancy because intrauterine infections have been shown to be strongly associated with certain complications of pregnancy. At the maternal—fetal interface, TLRs are expressed not only in the immune cells but also in nonimmune cells such as trophoblasts and decidual cells. Moreover, their expression patterns vary according to the stage of pregnancy. Here we will describe potential functions of TLRs in these cells, their recognition and response to microorganisms, and their involvement in the innate immunity. The impact of TLR-mediated innate immune response will be discussed via animal model studies, as well as clinical observations.
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