Characterization of anti-endothelial cell antibodies in the patients with systemic lupus erythematosus: a potential marker for disease activity.

To investigate the prevalence and possible role of anti-endothelial cell antibodies (AECA) in the pathogenesis of systemic lupus erythematosus (SLE), cell membrane antigen was prepared from cultured human umbilical vein endothelial cells and immunoblotting performed to detect AECA in SLE sera. IgG-AECA could be detected in 41 (86%) of 47 SLE patients. They were highly specific and failed to react with membrane antigens of human peripheral blood mononuclear cells or granulocytes. IgG-AECA reacted with endothelial membrane antigens which ranged from 15 to 200 kDa in molecular size. Further analysis of the antigens reacting with IgG-AECA revealed some interesting correlations between specific species of antibodies with certain clinical manifestations. Thus, patients having lupus nephritis, vasculitis, and hypocomplementemia had IgG-AECA against a 66-kDa membrane antigen; those with thrombocytopenia had IgG-AECA against a 55-kDa antigen; those with pleuritis had IgG-AECA against an 18-kDa antigen. These results indicate that IgG-AECA in the sera of SLE patients consist of heterogenous species.