Antiendothelial cell antibodies in patients with the antiphospholipid syndrome.

Antiendothelial cell antibodies (AECA) have been detected in 20 out of 30 patients (67%) with thrombosis associated with antiphospholipid antibodies. Seven patients had systemic lupus erythematosus and 13 had the "primary" antiphospholipid syndrome. Seven patients had both IgG and IgM AECA, 9 had IgG AECA only, and 4 had only IgM AECA. None of 30 control patients with thrombotic events not related to antiphospholipid antibodies had a positive titre of AECA (P less than 0.001). No correlation between AECA, antinuclear antibodies, anti-dsDNA antibodies, anti-neutrophil cytoplasm antibodies, precipitating antibodies to soluble nuclear and cytoplasmic antigens or complement components was found. The possible role of these AECA in the pathogenesis of thrombotic events is discussed.