Characterization and specificity of anti-endothelial cell membrane antibodies and their relationship to thrombosis in primary antiphospholipid syndrome (APS).

Immunoblotting was used to detect antibodies reacting with membrane and cytosol preparations of human umbilical vein endothelial cells (HUVEC), fibroblasts and a T lymphoma line HUT78 in 18 patients with anticardiolipin antibodies (ACA) (14 of whom had had a thrombotic event), 11 patients with a recent myocardial infarction and 17 controls. Multiple membrane-specific antibodies to HUVEC were found in 10 of the patients with ACA (28 bands) and in nine of the patients with thromboses (27 bands) in contrast to only three of the patients with myocardial infarction (four bands) and one control (one band). The most frequently recognized HUVEC membrane epitopes were at 33 kD (four sera), 61-63 kD (five sera) and 76-79 kD (four sera). Although cross-reactivity with fibroblast and/or HUT78 membranes was seen at 33 kD, binding at 61-63 kD and 76-79 kD was specific for endothelial membranes. Although no correlations with the presence and titre of ACA were seen, HUVEC membrane-specific antibodies showed a correlation with venous thrombotic events.