Antiphospholipid antibodies are a heterogeneous group of auto-antibodies (IgG, IgM, and IgA) initially thought to be specific only to negatively charged phospholipids. It is now well recognized that many antiphospholipid antibodies are directed to phospholipid-protein complexes and /or to proteins in the absence of phospholipids.
Antiphospholipid antibody cofactors are plasma proteins mostly with function in coagulation and strong phospholipid binding activities. Cofactors increase the binding of antiphospholipid antibodies in vitro and may help the development of thrombosis in vivo.