Trophoblast antigens, fetal blood cell antigens, and the paradox of fetomaternal tolerance

The paradox of fetomaternal tolerance has puzzled immunologists and reproductive biologists alike for almost 70 yr. Even the idea that the conceptus evokes a uniformly tolerogenic immune response in the mother is contradicted by the long-appreciated ability of pregnant women to mount robust antibody responses to paternal HLA molecules and RBC alloantigens such as Rh(D). Synthesizing these older observations with more recent work in mice, we discuss how the decision between tolerance or immunity to a given fetoplacental antigen appears to be a function of whether the antigen is trophoblast derived-and thus decorated with immunosuppressive glycans-or fetal blood cell derived. We review our current understanding of adaptive immune responses to the fetoplacental allograft, emphasizing the divergent responses observed for trophoblast- versus fetal blood cell-derived antigens. We suggest these divergent responses arise from cell type-specific glycosylation programs that impart trophoblast-derived antigens with immunosuppressive properties.

Automated summary

The paradox of fetomaternal tolerance has been a mystery to immunologists and reproductive biologists for nearly 70 years. By synthesizing older observations with recent studies, this article discusses the decision between tolerance or immunity to fetoplacental antigens based on their origin and glycosylation, highlighting the different responses observed for trophoblast-derived antigens compared to fetal blood cell-derived antigens.