Antibodies to beta 2-glycoprotein I and clinical manifestations in patients with systemic lupus erythematosus

Objective. To investigate whether anticardiolipin antibodies (aCL) in patients with systemic lupus erythematosus (SLE) bind to beta(2)-glycoprotein I (beta(2)GPI), and to search for a relationship between the presence of IgG and/or IgM anti-beta(2)GPI antibody and clinical manifestations in SLE patients. Methods. IgG and IgM anti-beta(2)GPI in 308 Japanese SLE patients were measured using phospholipid-independent enzyme immunoassays. Relationships to clinical histories and to various laboratory data were examined. Results. The values of anti-beta(2)GPI and aCL, as measured by conventional enzyme immunoassay, showed a strong correlation, but the anti-beta(2)GPI assay was more useful in distinguishing beta(2)GPI-dependent aCL from beta(2)GPI-independent a CL. The presence of IgG anti-beta(2)GPI was associated with an increased frequency of a history of thrombosis. Comparisons of various laboratory data suggested that the titer of anti-beta(2)GPI may fluctuate with disease activity. Conclusion. The results suggest that pathogenic aCL is directed against structurally altered beta(2)GPI and that enzyme immunoassay for anti-beta(2)GPI may prove useful in evaluating the risk of thrombosis and monitoring the clinical course in patients with SLE.