A Phospholipid-β2-Glycoprotein I Complex Is an Antigen for Anticardiolipin Antibodies Occurring in Autoimmune Disease But Not with Infection

Abstract

Anticardiolipin antibodies (aCL) purified from patients with autoimmune disease have recently been shown to interact with a phospholipid-binding plasma protein, β2-glycoprotein I (β2-GPI). The aim of this study was to determine whether aCL purified from patients with infection also interact with β2 -GPI. aCL purified from 23 patients with malaria, infectious mononucleosis, tuberculosis, hepatitis A or syphilis did not require the presence of β2-GPI to bind cardiolipin (CL). In contrast, aCL were purified from 11 out of 12 patients with autoimmune disease that bound CL only in the presence of β2-GPI. Thrombotic complications appear to be associated with aCL occurring in autoimmune disease but not with aCL associated with infections. We postulate that this increased risk of thrombosis in the autoimmune group may be due to the presence of aCL that bind CL in association with β2-GPI, a plasma protein with anticoagulant activity.