Antibodies to age-β2 glycoprotein I in patients with antiphospholipid antibody syndrome.

Antiphospholipid antibody syndrome (APS) is a systemic autoimmune disease clinically characterized by arterial and/or venous thromboses, recurrent abortions or fetal loss and serologically by the presence of "antiphospholipid antibodies" (aPL). The main target antigen of the antibodies is β2 glycoprotein I (β2 GPI). Post-translational oxidative modifications of the protein have been widely described. In this study we aimed to analyse sera reactivity to glucose-modified β2 GPI (G-β2 GPI). Sera collected from 43 patients with APS (15 PAPS and 28 SAPS), 30 with systemic lupus erythematosus (SLE), 30 with rheumatoid arthritis (RA) and 40 healthy subjects were analyzed by an enzyme-linked immunosorbent assay (ELISA) using a G-β2 GPI. Nine out of 15 consecutive PAPS out-patients (60%) and 16 out of 28 SAPS (57.1%) showed serum antibodies (IgG class) against G-β2 GPI (anti-G-β2 GPI) by ELISA. The occurrence of anti-G-β2 GPI was significantly higher in APS patients as compared to patients suffering from SLE. None of RA patients or control healthy subjects resulted positive for anti-G-β2 GPI. Of note, aG-β2 GPI prompted to identify some APS patients (4 PAPS and 7 SAPS), who were negative in the classical anti-β2 GPI test. Moreover, in APS patients, anti-G-β2 GPI titer was significantly associated with venous thrombosis and seizure in APS patients. This study demonstrates that G-β2 GPI is a target antigen of humoral immune response in patients with APS, suggesting that β2 GPI glycation products may contain additional epitopes for anti-β2 GPI reactivity. Searching for these antibodies may be useful for evaluating the risk of clinical manifestations. This article is protected by copyright. All rights reserved.