Further characterization of anti-endothelial cell antibodies in systemic lupus erythematosus by controlled immunoblotting.

Anti-endothelial cell antibodies in systemic lupus erythematosus were further characterized by controlled immunoblotting studies with EN4 defined membrane and cytosol preparations of human umbilical vein endothelial cells. Antibodies to endothelial cell membranes, some of which reacted with the membranes of both dermal fibroblasts and T-cell lymphoma HUT78, were detected in 26/33 patients (78%), but in only 4/34 normal controls (P < 0.001) and 3/11 patients with a recent myocardial infarction. Although the antibody response was very heterogeneous against epitopes ranging from 17 to 205 kDa, there was a tendency to detect particular membrane epitopes at 31-33 kDa (15 cases), 72-78 kDa (eight cases), 66-68 kDa (seven cases) and 17-19 kDa (five cases). No correlations between antibodies to particular epitopes and disease manifestations were observed nor was a relationship to disease activity detected in a retrospective analysis. However, the possibility that anti-endothelial cell antibodies may be pathogenically important was supported by prospective serial studies in two cases with nephritis who showed diminution and disappearance of anti-endothelial cell antibodies as their active disease was treated into remission.