Platelet autoantibodies detected by immunoblotting in systemic lupus erythematosus: Association with the lupus anticoagulant, and with history of thrombosis and thrombocytopenia

Abstract

71 patients with systemic lupus erythematosus (SLE) were studied for the occurrence of platelet antibodies by immunosblotting. Binding of IgG antibodies to platelet protein antigens was observed in 39 of the 71 patients. The most frequently detected and exceptionally strongly reacting antibodies were directed against platelet protein antigens with an approximate molecular weight of 65 kDa under nonreducing conditions. These antibodies were autoreactive and, when followed, they usually persisted. Interestingly, in this group of well-defined SLE patients, platelet antibodies against the most common targets (65 kDa) were significantly associated with the lupus anticoagulant, a history of thrombocytopenia and thrombosis, particularly with arterial occlusions. The lupus anticoagulant, on the other hand, correlated significantly only with venous thrombosis. In addition to the lupus anticoagulant, platelet antibodies against this unknown platelet protein may thus be a marker of a higher risk of thrombosis in SLE patients.