Role of anti-β2 glycoprotein I antibodies in antiphospholipid syndromeglycoprotein I antibodies in antiphospholipid syndromeIn vitro and in vivo studies

Antiphospholipid syndrome (APS) is characterized by the presence of recurrent venous/arterila thrombosis and fetal losses associated with a family of auto-antibodies directed against phospholipid (PL)-binding proteins. Among them, β2 glycoprotein I (β2GPI) is the most important. As a plasma cationic protein, β2 GPI binds to anionicPLs involved in several fluid-phase coagulation steps, and more importantly, it can be expressed on the surface of different cell types. Anti-β2 GPI antibodies recognize the molecule expressed on endothelial cells, platelets, monocytes, and trophoblast cells. Once bound, the antibodies trigger in vitro cell signaling that modulates biological responses potentially responsible for pathogenic mechanisms. Experimental animal models have supported the in vivo pathogenic role of anti-β2 GPI antibodies in both thrombosis and fetal loss models.