Mode of Action of the IgG Inhibitor of Erythropoiesis in Transient

Twelve cases of transient erythroblastopenia of childhood (TEC) have been studied to evaluate their marrow cell erythropoiesis in vitro and the effect on it of their serum or IgG. The number of colony-forming units-erythroid (CFU-E) and burst-forming units-erythroid (BFU-E) in the bone marrow of nine cases was extremely variable and did not allow any conclusion regarding the pathogenesis of this anemia. An IgG inhibitor of growth of erythroid colonies or bursts was detected in 8/12 cases. This IgG inhibitor had no effect on the growth of granulocyte-macrophage cobnies. Further studies on its mode of action indicated that the lgG did not have antierythropoietin antibody properties and did not affect the mature erythroblasts. as shown by a lack of inhibition of their response to erythropoietin and by