IgA class anti-β₂-glycoprotein I in patients with systemic lupus erythematosus

Objective. To search for a possible relationship between the presence of IgA class anti-β₂-glycoprotein I antibody (aβ₂-GPI) and clinical manifestations, including thrombotic episodes, in patients with systemic lupus erythematosus (SLE). Methods. Serum IgA aβ₂-GPI levels in 124 Japanese patients with SLE were measured using a phospholipid independent enzyme immunoassay. Relationships to clinical histories and to various laboratory data including IgG and IgM class aβ₂-GPI were examined. Results. Twenty-five percent of patients with SLE were positive for IgA aβ₂-GPI. Patients with a history of thrombosis had significantly higher probabilities for positivity of IgA aβ₂-GPI, compared to those without. The presence of IgA aβ₂-GPI was correlated with presence of lupus anticoagulant and/or biological false positive result for serological syphilis test. Titer of IgA aβ₂-GPI significantly correlated with values of IgG aβ₂-GPI, IgM aβ₂- GPI, and anti-DNA antibodies. Conclusion. The presence of IgA aβ₂-GPI may be related to the occurrence of thrombosis in patients with SLE. Measurements of IgA aβ₂-GPI may be of value for evaluating risk of thrombosis in patients with SLE.