Release of platelets into the circulation induced by gamma globulin treatment in a case of idiopathic thrombocytopenic purpura.

The kinetics and distribution in vivo of 111In-labelled platelets prior to and during intravenous high-dose gamma globulin therapy in a 3-months-old child with idiopathic thrombocytopenic purpura were evaluated. Concomitantly with a prompt increase in platelet concentration we found evidence for release of platelets into the circulation, presumably to a large extent originating from the spleen and liver. Our results support the concept that, in response to high-dose gamma globulin therapy, platelets are not only forced to remain in but are also released into the circulation, presumably as a result of mobilization of platelets adhering to cells of the monocyte-macrophage system.