ANTI-BETA(2)-GLYCOPROTEIN-I ANTIBODIES - DETECTION AND ASSOCIATION WITH THROMBOSIS

It has been demonstrated that antiphospholipid antibodies (aPL) recognize epitopes formed by anionic phospholipids and protein cofactors. beta 2 glycoprotein I (beta(2)GPI) is accepted as the cofactor of anticardiolipin antibodies (aCL). In the present study we explored the presence and clinical associations of anti beta(2)GPI antibodies of IgG isotype (a beta(2)GPI-IgG), measured by ELISA. We studied sera from 169 patients with aCL and/or lupus anticoagulant (LA), including 52 patients with systemic lupus erythematosus and 49 with primary antiphospholipid syndrome (PAPS). We found 31.9% positive sera for a beta(2)GPI-IgG in the whole population and 48.6% in the aCL-IgG(+) group. There was a good correlation between the titre of aCL-IgG and the optical density for a beta(2)GPI-IgG (r = 0.69, P < 0.01). The presence of a beta(2)GPI-IgG was associated with the presence of aCL-IgG (P < 0.0001) and LA (P < 0.0005). However, none of 23 LA (+) patients without aCL had a beta(2)GPI-IgG. We found a statistically significant association between the presence of a beta 2GPI-IgG and a history of venous thromboembolism (VTE) in our patients (P < 0.005). This association was observed in PAPS (P < 0.05) but not in secondary antiphospholipid syndrome (SAPS). Our study confirms that some aPL(+) sera react with beta(2)GPI in special experimental conditions. In addition, the presence of these antibodies is associated with a history of VTE.