Do IgA antiphospholipid antibodies have any clinical importance?

Antiphospholipid antibodies (aPL) are strongly associated with clinical manifestations of the antiphospholipid syndrome (APS) such as thromboembolic events and/or pregnancy loss. IgG anticardiolipin (aCL) at moderate/high titre and IgG anti-β2-glycoprotein I (aB2GPI) are closely related to clinical complications, IgM are commonly transient, present during infections, while IgA are not routinely tested. The aim of our study was to evaluate the occurence and possible clinical significance of the IgA isotype of four different aPL: aCL, aB2GPI, anti-prothrombin (aPT) and anti-annexinV (aANXV) antibodies. Sera from 92 patients (87 females and 5 males) with systemic autoimmune disorders (63 with systemic lupus erythematosus (SLE), 19 with secondary APS (SLE with APS) and 10 with primary APS (pAPS)) were assayed with four different in-house ELISA tests. For each of the four antibodies IgG, IgM and IgA isotypes were determined. In evaluating the association of isotypes with particular clinical features (arterial and venous thromboses, CNS disorders, abortuses, thrombocytopenia), IgA isotype did not improve the clinical sensitivity of any measured antibody. The IgA aB2GPI were the only aPL occuring alone in a significant number of patients. Such patients should be followed-up to provide insight into the possible clinical significance of IgA aB2GPI.