A Class I Antigen, HLA-G, Expressed in Human Trophoblasts

TLDR

The HLA‑G α chain was characterized as five 37‑ to 39‑kDa isoforms using two‑dimensional gel electrophoresis. HLA‑G is highly expressed in first‑trimester villous cytotrophoblasts, decreases in the third trimester, shows no allelic variation, is present in JEG but not Jar or BeWo choriocarcinoma cells, is absent in normal lymphoid cells, and is regulated in a cell‑type and developmental‑stage–specific manner.

Abstract

The α chain of the human histocompatibility antigen HLA-G was identified as an array of five 37- to 39-kilodalton isoforms by the use of two-dimensional gel electrophoresis. Both cell-associated and secreted HLA-G antigens are prominent in first trimester villous cytotrophoblasts and are greatly reduced in third trimester cytotrophoblasts. Allelic variation was not detected, an indication that HLA-G is not obviously polymorphic in cytotrophoblasts. Among the following choriocarcinoma cell lines studied, HLA-G is expressed in JEG but not in Jar or BeWo. Expression of endogenous HLA-G genes has not been found in normal lymphoid cells. Thus, HLA-G is subject to both cell type-specific and developmental regulation and is expressed in early gestation human cytotrophoblasts.