Mechanisms of T cell tolerance towards the allogeneic fetus

Recent work in mice has revealed several mechanisms that either minimize the activation of maternal T cells with fetal or placental specificity, or minimize the possibility that such T cells, if activated, can harm the fetus.First, there is an absence of direct allorecognition of paternal MHC molecules expressed by cells of the conceptus.Second, dendritic cells are trapped within the decidua, thereby minimizing the immunogenic presentation of conceptus-derived antigens in the uterine draining lymph nodes.Third, regulatory T cells suppress T cell activation in response to conceptus-derived antigens.Fourth, epigenetic silencing of chemokine genes occurs in decidual stromal cells, which prevents activated T cells from accumulating at the maternal–fetal interface.