Immunologic Studies on the Mechanism of Action of Erythropoietin.

Abstract

Injections into normal mice of serum obtained from rabbits previously immunized with human urinary erythropoietin results in a progressive daily decrease in the relative numbers of erythroid cells in the bone marrow. Injections of this serum into polycythemic mice 24 to 44 hours after initiation of a wave of erythropoiesis with erythropoietin has no effect on the magnitude of the erythropoietic response, although injections of the serum one hour before or at the same time that exogenous erythropoietin is administered completely abolish the erythropoietic response. These results support the concepts that erythropoietin is involved in normal regulation of red cell production and that this regulation is the result of the effect of erythropoietin on the differentiation of stem cells.