Antigen Specificity of Antiphospholipid Syndrome-Related Antiphospholipid Antibodies

ABSTRACT

The antiphospholipid syndrome (APS) is an autoimmune disorder characterized by the presence of antiphospholipid antibodies (aPL) and clinically by vascular thrombosis and/or recurrent pregnancy morbidity. The APSassociated aPL are mostly directed against β₂-glycoprotein I (β₂GPI) and prothrombin. In contrast, aPL linked to infectious disorders are primarily directed against phospholipids and do not tend to be associated with the clinical manifestations of APS. This distinction, however, was later found not to be absolute. Patients with lepromatous leprosy have a high prevalence of true antibodies to β₂GPI, but they do not develop thromboembolic complications. Current evidence suggests that autoantibodies to β₂GPI from APS patients preferentially bind to critical epitopes in domain I of β₂GP1, and leprosyrelated aPL recognizing β₂GPI tend to be directed against domain V. The position of the epitope in the β₂GPI molecule seems to be crucial in defining the pathogenicity of aPL. In addition, an increasing number of other phospholipids-binding proteins with central functions in the regulation of blood coagulation and fibrinolysis are also targeted by APS-related autoantibodies. This review intends to highlight the diverse antigen specificity of aPL and likely further studies would help to understand the different clinical behavior of patients with APS and infections-related aPL.

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