DO PATIENTS WITH ANTIPHOSPHOLIPID SYNDROME HAVE AUTOANTIBODIES TO BETA(2)-GLYCOPROTEIN-I

High positive anticardiolipin antibody tests have been associated with recurrent thrombosis and pregnancy loss. Although these antibodies we re believed to bind negatively charged phospholipids, recent reports h ave suggested that a serum protein, beta2-glycoprotein I (beta2-GPI), may be the true antigen for these antibodies. To resolve this issue, w e compared binding of 75 anticardiolipin-positive and 71 anticardiolip in-negative serum samples from patients with rheumatic diseases to bet a2-GPI by using an enzyme-linked immunosorbent assay (ELISA). Serum sa mples from 30 healthy blood donors and 10 laboratory personnel were us ed as normal controls. We found no difference in binding between the t hree groups of serum samples. In addition, when binding to beta2-GPI c oated plates was compared with binding to ELISA plates without beta2-G PI (blank), no difference was observed. Finally, binding of anticardio lipin-positive serum samples to plates coated with cardiolipin-beta2-G PI mixture varied directly with the cardiolipin concentrations. Based on these findings, we conclude that anticardiolipin-positive serum sam ples do not bind beta2-GPI.