Studies on the Regulation of Granulopoiesis. IV. Possible Humoral Regulation

Abstract Serum obtained from mice after irradiation shows an enhanced ability to stimulate growth of granulocytic colonies in vitro. This enhanced stimulatory ability of serum is related in both time and magnitude to the neutropenia developing after irradiation and in time to the granulopoietic response of the marrow to the neutropenia. The relationship suggests that the active factor in postirradiation serum might be granulopoietin, the physiological regulator of granulopoiesis.