Secondary anti-phospolipid syndrome (APS) is diagnosed in many patients with systemic lupus erythrematosus (SLE) especially with thromboembolic events and/or pregnancy loss in the presence of persistent laboratory evidence for anti-phospholipid antibody (aPL). In this work, we aimed to detect the prevalence of IgG and IgA anti-β2 glycoprotein1 (β2GP1) in SLE patients. Serum samples were collected from 50 female patients with SLE (25 had APS and 25 patients who did not have APS), in addition to 22 apparently healthy females with matched age as a control group. All samples from patients and control were tested for lupus anticoagulant (LA), IgG and IgA isotypes of antiβ2GPI, Anti-nuclear antibody (ANA), Anti-double strand antibody (Anti-dsDNA). Number of patients positive for Anti-β2GP1 antibodies were significantly increased in APS patients compared to non-APS patients (P=0.015). Anti-β2GP1 IgA isotype was significantly higher in APS patients than in non-APS patients (P=0.011) and significantly correlated with deep venous thrombosis and pregnancy morbidity (P=0.004). There was no difference in anti-β2GPI IgG isotype between APS patients and non-APS patients. We concluded that although anti-β2GPI IgA is not within Sapparo diagnostic criteria, it seems to contribute to the pathogenesis of thrombotic manifestations of SLE and may represents a useful indicator particularly when standard aPL tests are negative.
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