Human Trophoblast‐Specific Surface Antigens Identified Using Monoclonal Antibodies*

Abstract
Mouse monoclonal antibodies have been produced against syncytiotrophoblast plasma membrane preparations isolated from term human placentas. Of 20 positive clones, two antibodies (H309, H318) were directed against the Cγ2 domain of IgG, one (H312) was directed against albumin, and another (H303) was directed against a further normal human serum component (not transferrin). One monoclonal antibody (H310) recognized an antigenic epitope restricted to trophoblast and lymphocytes: this antibody did not inhibit mitogenic or allogeneic stimulation of lymphocytes. Two monoclonal antibodies (H315 and H317) reacted with trophoblast‐specific antigenic determinants. The H315 antigen was present on first trimester syncytiotrophoblast, unlike the H317 antigen.