[Antiphospholipid and anti beta 2-glycoprotein I antibodies]

Recent studies have shown that beta 2glycoprotein I (beta 2GPI), a plasma inhibitor of coagulation with affinity for anionic phospholipids, is frequently required for the formation of the epitopes recognized by some anti-phospholipid antibodies. Six murine monoclonal antibodies directed against human beta 2GPI were compared with anti-beta 2GPI antibodies associated with systemic lupus erythematosus and primary anti-phospholipid syndrome. The beta 2GPI-dependent binding properties to neutral and anionic phospholipids were studied, as well as the target epitopes on the beta 2GPI molecule and the effect of various beta 2GPI treatments to get rid of contaminating phospholipids or to block the beta 2GPI-phospholipid interaction. The results are in favour of a direct binding of patient's antibodies to beta 2GPI, in the absence of phospholipids. Anti-beta 2GPI monoclonal antibodies, two of which inhibited beta 2GPI recognition by the antibodies from patients, possessed lupus-like anticoagulant properties, thereby constituting an interesting model for a subset (beta 2GPI-dependent) of anti-phospholipid antibodies.