ANTIBODIES AGAINST PLATELET-ACTIVATING-FACTOR IN PATIENTS WITH ANTIPHOSPHOLIPID ANTIBODIES

We have studied the specificity of antiphospholipid antibodies in 148 patients with autoimmune diseases, 120 patients with systemic lupus er ythematosus and 28 with the primary antiphospholipid syndrome. In addi tion, 20 patients suffering from syphilis were studied. As a control g roup, 64 healthy volunteers were investigated. Patient and control ser um samples were tested for binding to seven different phospholipid ant igens by ELISA. Interestingly, 90% of the sera from syphilis patients and 6% of the autoimmune patients exhibited a significant binding to p latelet-activating factor (PAF), a molecule similar to the structure o f phosphatidylcholine. In addition, the IgG fraction from one of the l upus patients, which showed a high binding activity to PAF, was furthe r affinity-purified using both liposomes and an affinity chromatograph y column. Preincubation of these antibodies with PAF inhibited subsequ ent binding to immobilized PAF. These observations might suggest a put ative interaction of antiphospholipid autoantibodies with PAF 'in vivo ', which may have, in some patients, important pathophysiological cons equences.