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.