HLA-G expression in trophoblast cells is independent of embryonic development

HLA-G is a nonclassical major histocompatibility complex class I molecule t hat is selectively expressed;on cytotrophoblasts at the feto-maternal inter face where ii may play a major role in maternal-fetal tolerance. In this st udy, we compared HLA-G expression in trophoblasts from normal and pathologi c pregnancies by immunohistochemical analysis. First, we found a defective HLA-G expression in miscarriages associated with hypotrophic but normal egg s. Conversely, by studying molar pregnancies, we observed a high HLA-G expr ession in-complete and partial hydatidiform moles. Finally, HLA-G expressio n could be visualized in extravillous trophoblasts that develop outside of their normal environment, as reported here in ectopic pregnancies. Taken to gether, these results suggest that HLA-G expression in extravillous trophob lasts is induced in an autonomous manner, independently of embryonic develo pment, and may be an integral pare of placental development allowing its to lerance from maternal immune system. (C) American Society for Histocompatib ility and Immunogenetics, 2000. Published by Elsevier Science Inc.