Objectives Beta 2 glycoprotein was identified as a cofactor for the binding of antiphospholipid antibodies. Anticardiolipin antibodies were found to correlate with thrombosis in SLE patients. We measured the subclasses of anti B2 GP1 in LSE patients with or without history of thrombosis.

Methods Fourty four SIE patients with mean (± SD) age of 26.7 ± 9.9) years, nine of whom had a history of vascular thrombosis along with 30 healthy age and sex matched normal control subjects were studied.

Results There was a correlation between the presence of IgG anti B2 GP I and the incidence of thrombosis (P < 0.05), There was, also, a positive correlation between IgG anti B2 GPt and IgG aCL antibodies and a negative correlation between IgG anti B2 GP1 and thrombocytopenia. However, serum levels of IgG and 1 gM anti B2GPI were increased in patients who had positive LAC activity. This thesis confirm the pathologic role of IgG anti B 2 GP1 (and not 1gM) in the incidence of thrombosis in SLE patients. Also, its relationship to the presence of anti ds DNA antibodies, anti CLA and lupus anticoagulant in SIE is discussed.