Evidence for a novel HLA antigen found on human extravillous trophoblast and a choriocarcinoma cell line.

We describe the characterization of a novel HLA Class I molecule, which we have isolated from chorionic cytotrophoblast cell membranes, and from a trophoblast-derived choriocarcinoma cell line, BeWo; classical HLA Class I antigens are not expressed on these cells. This antigen is an electrophoretically non-polymorphic glycoprotein of approximately 40,000 molecular weight, which is found in association with beta 2 microglobulin, and which is detected by monoclonal antibodies recognizing monomorphic determinants of HLA Class I. Elucidation of the nature and origin of this molecule may provide valuable information regarding the immune barrier that exists between mother and fetus.