Platelet antibody binding and spontaneous aggregation in 21 lupus anticoagulant patients.

In order to ascertain the role of the antiphospholipid antibody in the pathogenesis of thrombotic disorders, a study of 21 lupus anticoagulant-positive patients was done by a number of serologic and functional platelet tests. In immunofluorescent studies, we found that 80% showed a mitochondrial pattern on HEp cells and all patients gave an ubiquitously intense staining of donor platelets. By a microscopic spontaneous aggregation test, all lupus anticoagulant-positive patients showed accelerated platelet aggregation which was calcium-independent. The results show that the plasma of lupus anticoagulant-positive patients contains a platelet-binding antibody and causes spontaneous agglutination of platelets. These properties may play a role in the thrombogenesis common to the antiphospholipid syndrome.