Phospholipid-dependent anti-β₂-glycoprotein I (β₂-GPI) antibodies and antiphospholipid syndrome

A portion of anticardiolipin antibodies is defined as phospholipid-dependent anti-β₂-glycoprotein I (β₂-GPI) antibodies and recognizes the conformationally altered β₂-GPI which interacts with anionic phospholipids. We studied the clinical significance of IgG phospholipid-dependent anti-β₂-GPI antibodies in patients with antiphospholipid syndrome (APS). The subjects consisted of 60 APS patients. IgG phospholipid-dependent anti-β₂-GPI antibodies were detected by ELISA in 32 of the 60 patients (53%). Significantly higher incidences of prolonged APTT and lupus anticoagulants were found in patients with these anti-β₂-GPI antibodies. Moreover, significantly lower incidences of malar rash, serositis, LE cell preparation and anti-Sm antibodies were found in patients with these anti-β₂-GPI antibodies. It was found that 88% of the patients with these anti-β₂-GPI antibodies satisfied less than five of the revised criteria items for the classification of SLE. These findings indicate the clinical characteristics of APS patients with IgG phospholipid-dependent anti-β₂-GPI antibodies.