The relationship of anti-endothelial cell antibodies to anti-phospholipid antibodies in patients with giant cell arteritis and/or polymyalgia rheumatica.

Sera from patients with giant cell arteritis and/or polymyalgia rheumatica were tested for the presence of IgG, IgM and IgA antibody to endothelial cells (AEC), cardiolipin (ACL) and phosphatidylethanolamine (APE) using enzyme-linked immunosorbent assays. There were strong correlations between ACL and APE, but also between AEC and ACL IgM (p < 0.02) and between AEC and APE IgA (p < 0.003). Inhibition of AEC binding was achieved by absorption onto EC, but ACL and APE binding was also significantly reduced. In contrast, the binding of AEC antibody could not be inhibited by incubation with CL. Our data suggest that AEC constitute a heterogeneous population of autoantibodies.