الفهرس 
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Abstract
Thrombophilia is defined as a predisposition or susceptibility to thrombosis. It may be congenital, acquired or mixed congenital and acquired. Immune mediated thrombosis is considered among the acquired causes of thrombophilia. Ag-Ab mediated reactions play a critical role in the pathogenesis of thrombotic events in different syndromes representing the immune mediated thrombosis including Antiphospholipid antibody syndrome, Heparin induced thrombocytopenia, and Thrombotic thrombocytopenic purpura. Antiphospholipid Antibody Syndrome is the most common cause of acquired thrombophilia; at a prevalence of 1 to 5 percent for both aCL antibodies and LA antibodies. aPL are directed against plasma proteins that bind to anionic phospholipids. Several phospholipid-binding proteins have been identified but β2-GPI is believed to be the major target of these antibodies. Several hypotheses have been proposed to explain the cellular and molecular mechanisms by which aPL promote thrombosis. Two types of assays are used for the detection of aPL antibodies: coagulation assays, in which LAs are detected by their ability to prolong phospholipid-dependent coagulation reactions, and immunoassays, in which aCLs and antibodies against other phospholipids and protein cofactors are detected most commonly by ELISA. Coagulation assays include aPTT, Kaolin clotting time and diluted Russell’s viper venom time. Immunoassays include aCL ab, anti β2 GPI and antiprothrombin antibodies.