Stimulation of granulopoiesis by liver macrophages

Isolated murine Kupffer cells or liver macrophages release high levels of colony-stimulating activity (CSA) necessary for the proliferation of granulocytic and mononuclear cell colonies in vitro. CSA was detected in media conditioned by Kupffer cells ata concemtration of 0.25 x 10'6 cells per millilter. Conditioned media from suspensions of unseparated liver did not stimulate colony formation and, in high concentrations,were inhibitory. CSA obtained from Kupffer cells was more active on a cell percell basis than CSA OBTAINED FROM LUNG OR PERITONEAL MACROPHAGES. These studies indicate that liver macrophages can also release CSA and further support the concept that the monocyte-macrophage system may play a role in the regulation of granulopoiesis.