PRESENCE OF A PLATELET AGGREGATING FACTOR IN THE PLASMA OF PATIENTS WITH THROMBOTIC THROMBOCYTOPENIC PURPURA (TTP) AND ITS INHIBITION BY NORMAL PLASMA

Abstract

Three patients with TTP were treated by infusion of normal plasma with dramatic responses. The plasmas collected from these patients during relapse induced in vitro aggregation of washed platelets from both normal donors and the patients from both normal donors and the patients during remission. The platelet aggregating factor was not dialyzable or adsorbable by Al(OH)3 and was not inactivated by DFP, hirudin or heparin with normal amounts of antithrombin. In contrast to the platelet aggregation induced by platelet isoantibody, the platelet aggregating activity of TTP plasma diminished as a function of time when it was incubated with normal plasma at 37.degree. C. At least some instances of TTP appear to be due to deficiency of a plasma inhibitor to counteract a platelet aggregating factor demonstrated in the plasma of these patients.