Association of anti-beta 2 glycoprotein I antibodies with lupus-type circulating anticoagulant and thrombosis in systemic lupus erythematosus.

PURPOSE: Antiphospholipid antibodies (including anticardiolipin antibodies and circulating anticoagulant) are associated with thrombosis in systemic lupus erythematosus. Since it has been shown that beta 2 glycoprotein I (beta 2 gp I) acts as a cofactor of anticardiolipin antibody binding to cardiolipin, the presence and clinical meaning of anti-beta 2gp I antibodies in sera from patients with lupus were examined.

PATIENTS AND METHODS: An enzyme-linked immunosorbent assay technique for the detection of anti-beta 2gp I antibodies was developed, and 47 lupus sera were studied retrospectively, as well as 88 healthy blood donors' sera.

RESULTS: It was found that 17 of 47 patients with lupus (36%) had anti-beta 2gp I antibodies. Anti-beta 2gp I antibodies were statistically associated with anticardiolipin antibodies, thrombosis, and lupus anticoagulant. Eight of nine lupus patients with thrombosis had anti-beta 2gp I antibodies and lupus anticoagulant, and seven of them had anticardiolipin antibodies. Of 18 patients with anticardiolipin antibodies without anti-beta 2gp I antibodies or lupus anticoagulant, only one had thrombosis (due to nephrotic syndrome). Among anti-beta 2gp I-positive patients, 14 of 16 had lupus anticoagulant activity, whereas only three patients with lupus anticoagulant were anti-beta 2gp I-negative.

CONCLUSIONS: The presence of anti-beta 2gp I antibodies is a new immunologic feature of lupus patients with thrombosis. In addition, since anti-beta 2gp I antibodies are closely associated with lupus anticoagulant activity, they may contribute to explain antiprothrombinase activity.