The use of intravenous γ-globulin in idiopathic thrombocytopenic purpura
Bronchoalveolar Lavage Fluid
In 1981, Imbach et al. (Lancet, 1, 1228-1231) reported that infusion of intravenous immunoglobulin (IVIG) would substantially elevate platelet counts in children with acute or chronic idiopathic thrombocytopenic purpura (ITP). Subsequent studies confirmed these findings and extended the effect to adults and to newborns with passive immune thrombocytopenia. Studies in children with acute ITP demonstrated that administration of IVIG was the fastest way to increase a patient's platelet count, and that this agent could be given at doses as high as 1 g/kg/day so that the course of therapy and response to treatment would be more rapid. Reports of effective treatment of patients with autoimmune neutropenia and autoimmune hemolytic anemia by IVIG broadened the scope of its usefulness. In addition, several studies in children and adults with chronic ITP suggested that repeated infusions were a safe and effective way to maintain an adequate platelet count in such patients, and might also gradually lead to lasting improvement. These studies and Imbach's controlled trial in children with acute ITP suggested that IVIG therapy might provide a curative effect in addition to the acute effect. To combine all of these clinical effects with a multitude of in vitro observations to explain the mechanism of action of IVIG is complicated. Fehr et al. (N. Engl. J. Med. 306, 1254-1258, 1982) showed that Fc receptor blockade occurs following administration of IVIG. This effect is clearly demonstrated in vivo by the delayed removal from the vascular space of antibody-coated red blood cells following infusion of IVIG. In addition, many less well-defined effects occur in relation to immunoglobulin production, induction of suppressor cells, antiplatelet antibody levels, and bone marrow platelet production. Studies continue to try to define which effects actually underlie the clinical effects seen, and which are merely test-tube phenomena.