Annexin A2 (ANXA2), an endothelial cell receptor for plasminogen and tissue plasminogen activator, has been identified as a new autoantigen in antiphospholipid syndrome (APS).
Over-expression of A2 is seen in acute promyelocytic leukemia during the early hemorrhagic phase, while high titer antibodies to A2, as in antiphospholipid syndrome or cerebral venous thrombosis, are associated with thrombosis.
In humans, overexpression of A2 by acute promyelocytic leukemia cells is associated with excessive fibrinolysis and hemorrhage, whereas anti-A2 autoantibodies appear to accentuate the risk of thrombosis in patients with anti-phospholipid syndrome.