The maternal-fetal interaction: some controversies and solutions.

Recent studies have identified some of the mechanisms responsible for protecting the mammalian embryo against the potentially hostile immunological maternal environment. It is also apparent that these mechanisms vary at different stages of reproduction, from fertilisation to implantation and to full development of the fetus. They are also unique since they vary from species to species and result from exceptional genetic and immunological processes. In this review, a few controversial topics have been selected for discussion. They include the role of suppressive factors and cells, the transfer of immunocompetent cells across the placenta, and claims that habitual recurrent abortion may result from the absence of a maternal immune response.