EXPRESSION OF PHOSPHATIDYLSERINE-DEPENDENT ANTIGENS ON THE SURFACE OFDIFFERENTIATING BEWO HUMAN CHORIOCARCINOMA CELLS

PROBLEM: Antiphospholipid antibodies (aPLs) are associated with pregna ncy loss, pregnancy-induced hypertension, and intrauterine growth reta rdation. We have previously reported that phosphatidylserine (PS)-depe ndent antigens are expressed in formalin-fixed cells concurrent with d ifferentiation in a choriocarcinoma model (BeWo) of cytotrophoblast, T hat study, however, could not differentiate between cytoplasmic or sur face antigen expression. METHOD: Three monoclonal aPLs that differenti ate between PS- and cardiolipin (CL) dependent antigens were reacted w ith BeWo, with or without forskolin activation, before fixation, and a ntibody binding was evaluated by immunoperoxidase techniques. RESULTS: Activation with forskolin induced a PS-dependent antigenic determinan t on the surface on BeWo cells. CL-reactive monoclonal antibodies did not react with the cell surface, whether forskolin treated or not. CON CLUSION: These observations demonstrate that a PS-dependent antigen is expressed on the surface of a model of differentiating cytotrophoblas tic cells and should be accessible in vivo to circulating aPLs.