ROLE OF BETA(2)-GLYCOPROTEIN-I IN THE ANTIPHOSPHOLIPID ANTIBODY-BINDING TO ENDOTHELIAL-CELLS

A group of anticardiolipin antibodies (aCL) require beta(2)-glycoprote in I (beta(2)GPI) to recognize their target, which might be located on endothelial cells (EC) and/or platelets. Following incubation with ep ithelial cells, 13 of 30 lupus sera retained EC-reactive antibodies of the IgG, IgA and IgM isotypes. Associated aCL and anti-phosphatidylet hanolamine antibodies were partly absorbed on eC as well as EC. The fo rmer antibodies were more efficiently removed in the presence than in the absence of the latter. The presence of beta(2)GPI in the affinity- purified aCL preparations may explain their binding to EC, as this cro ss-reaction was abrogated by the removal of the cofactor and restored by its re-introduction. Seventy four per cent of EC were faintly stain ed with polyclonal or monoclonal antibody directed to the cofactor. Th e beta(2)GPI mediated aCL binding to EC membranes could thus be influe ntial in the development of thrombosis and/or thrombocytopenia in aCL- positive patients.