Role of β2-glycoprotein I in the anticardiolipin antibody affinity for phospholipid in autoimmune disease

Abstract

The binding capacity to cardiolipin and the functional affinity of affinity-purified anticardiolipin (aCL) IgG of patients with autoimmune disease have been compared with those of individuals with malaria and acquired immunodeficiency syndrome (AIDS). The binding of autoimmune IgG aCL was enhanced gradually by the incorporation of increasing amounts of β2-glycoprotein I (β2GPI) into the assay, in contrast to that of patients with infectious diseases. In addition, there were significant reductions of functional affinity in autoimmune disease, but not in malaria or in AIDS. These results indicate that β2GPI requirement for binding to the target antigen varies inversely with functional affinity in autoimmune disease when β 2GPI was present, and suggest that IgG aCL are more heterogeneous in this type of disorder than in patients with infectious disease.