Significance of IgA antiphospholipid antibodies.

IgA anticardiolipin (IgA aCL) and IgA anti beta2-glycoprotein-I (IgA anti beta2GP1) antibodies are common in SLE and have been associated in some studies with thromboses and thrombocytopenia. Experimental work suggests that IgA aCL are as prothrombotic as the IgG-IgM isotypes. However, in SLE there appears to be less concordance between IgA aCL and IgA anti beta2GP1 as compared with the concordance between IgG and IgM isotypes, suggesting significant differences in their origins and specificities. For example, there may be a greater mucosal contribution to production of IgA antibeta2GP1 than IgA aCL. Infections may have a greater role in the presence of IgA aCL than IgA antibeta2GP1 antibodies.