Temporary suppression of circulating antiplatelet alloantibodies by the massive infusion of fresh, stored, or lyophilized platelets.

Survival of 51Cr-labeled allogenic platelets was repeatedly measured in rabbits previously sensitized by weekly intradermal injections of platelets from donor animals. When values of recovery and survival time were reduced to very low levels, a massive infusion of platelets from randomly selected donor rabbits was given and survival study was repeated. A large increase in platelet survival and recovery was seen in every experiment. Similar results, although of lesser magnitude, were obtained with the infusion of platelets made nonviable by prolonged storage and, also, of lyophilized platelets. A significant increase in life span and recovery of allogenic platelets was also observed in two patients with thrombocytopenia due to aplastic anemia, severely allosensitized to platelets. After one massive infusion of viable or of nonviable platelets, survival and hemostatic effectiveness of subsequently infused allogenic platelets was greatly improved in both patients. Experimental blockade of the RES and titration of the serum alloantibody by the 14C-serotonin release method demonstrated that the favorable effect of the massive platelet infusions was due to the temporary adsorption of the alloantibody in the circulation of the sensitized animals. This two-step procedure of one massive infusion of viable, nonviable or lyophilized allogenic platelets followed by a small infusion of freshly collected platelets may be of practical value in arresting hemorrhage in selected thrombocytopenic patients refractory to all types of available donor platelets because of severe and complex alloimmunization.