Frontiers in Bioscience-Elite (FBE) is published by IMR Press from Volume 13 Issue 2 (2021). Previous articles were published by another publisher on a subscription basis, and they are hosted by IMR Press on imrpress.com as a courtesy and upon agreement with Frontiers in Bioscience.
For several decades, people have wondered why pregnant mothers do not reject fetuses bearing allogeneic paternal antigens. Several hypotheses have been proposed, including a physical barrier between fetuses and mothers, immaturity of fetal antigens and temporary dormancy of the maternal immune system. Based on the "cell death immune recognition model," the author proposes a hypothesis that pregnancy tolerance is an active immune response of the maternal immune system, which is induced by apoptotic cells bearing paternal antigens. The primary steps in the induction of pregnancy tolerance are apoptosis of fetal cells as well as spermatozoa; phagocytosis of those dying/dead cells by maternal antigen presenting cells (APC), migration of APC to local lymph nodes, antigen presentation and induction of regulatory T cells in local lymph nodes. The hypothesis outlined below will not only help us to understand how pregnancy tolerance is induced, but also provide novel strategies to develop clinical measures for patients with infertility or pregnancy-related disorders.