Actively induced platelet-bound IgG associated with thrombocytopenia in the marmoset

Interspecies platelet immunizations among marmosets lead to antibody formation to the donor platelets and a profound thrombocytopenia, which when associated with anemia may result in death of the animal. This actively induced immunologic thrombocytopenia closely resembles two clinical disease entities manifesting autoimmune thrombocytopenia, posttransfusion purpura and idiopathic thrombocytopenic purpura. Although antibody to donor-type platelets could be demonstrated readily, antihost activity was most often nondetectable or, when present, was in very low titer. A consistent finding was the appearance of IgG on the host's platelets shortly after immunization and concomitant with the appearance of antidonor platelet antibody. In 3 of 13 immunized animals thrombocytopenia did not occur even though antibody was formed and the host's platelets became lgG positive. In those animals that re-covered from the induced thrombocytopenia lgG-positive platelets were found for periods ranging from 30 to greater than oo days. Splenectomy before or after immunization did not alter the sequential development of antibody formation, appearance of lgG-positive platelets, and