Antiphospholipid antibodies in systemic lupus erythematosus and the antiphospholipid syndrome

The family of autoantibodies known as antiphospholipid antibodies (aPL) and the lupus anticoagulant (LA) are associated with a spectrum of clinical manifestations including life-threatening thrombosis. While our current knowledge of thrombosis is imperfect and the mere presence of aPL is imprecisely associated with clinical events, our knowledge in this area has greatly expanded in recent years. It is clear that high levels of IgG aPL are associated with an increased risk of thrombosis. In 1990, investigators demonstrated that some aPL are directed against the beta2-Glycoprotein I (beta2-GPI) 50 kDa subunit and reported that these showed concordance with risk of clotting in certain groups of patients. Studies have also demonstrated that aPL reacted with antigens other than beta2-GPI, namely prothrombin, annexin V, protein S, protein C and high molecular weight kininogen. We review the clinical features of the antiphospholipid syndrome (APS), including vascular occlusion, pregnancy loss, thrombocytopenia and catastrophic APS. We also review the role of antibodies in the pathogenesis of APS as well as the spectrum of autoantibodies that have been found in APS.