Some antiphospholipid antibodies bind to hemostasis and fibrinolysis proteases and promote thrombosis

It is generally accepted that the major autoantigen for antiphospholipid antibodies (aPL) is β2glycoprotein I (β2GPI). Interestingly, some aPL bind to β2GPI and the homologous enzymatic domains of several proteases involved in hemostasis and fibrinolysis, and correspondingly hinder anticoagulant regulation and resolution of clots. These findings are consistent with several early findings of aPL and provide a new perspective about some aPL in terms of their binding specificities and related functional properties in promoting thrombosis. In addition, homologous enzymatic domains of the involved proteases share conformation epitope(s) with β2GPI, thus providing a possible structural basis for some non-mutually exclusive mechanisms of aPL-mediated thrombosis.