IgG binding to endothelial cells in systemic lupus erythematosus.

Endothelial-associated IgG were determined in 20 patients with systemic lupus erythematosis (SLE)-8 of whom had a lupus anticoagulant (LA) and 6 a history of thrombosis. The binding of IgG present in patient plasma to cultured human endothelial cells was detected using radiolabeled staphylococcal protein A. Thirteen samples gave positive results and a significant association between endothelial-associated IgG and lupus anticoagulant was found (p less than 0.05). No statistically significant relationship with a previous history of thrombosis was found. These results suggest that the lupus anticoagulant may be directly involved in immune vascular injury induced by either antibodies or immune complexes in SLE.