Abstract
β2-Glycoprotein I (β2GPI), a phospholipid-binding protein, is one of the major target antigens for antiphospholipid antibodies (aPL) found in patients with antiphospholipid syndrome (APS). Thrombophilic disorders in APS patients are strongly associated with aPL, and their pathogenic properties depend on the presence of β2GPI. Procoagulant cell stimulation by aPL, via β2GPI, is one of the most plausible mechanisms of thrombosis in APS, and p38 mitogen activated protein kinase (MAPK) pathway plays a crucial role in such activation. β2GPI is proteolytically cleaved in domain V by activated factor X or plasmin, leading to the generation of the nicked form of β2GPI. Recently, increasing attention is focused on the role of nicked-β2GPI as a regulator of extrinsic fibrinolysis pathway.