Enhancement of the action of colony stimulating factor (CSF) by soluble component(s) of erythrocytes in mouse bone marrow cells cultures.

Rat erythrocytes, separated from other blood cells by SE-cellulose chromatography, were lysed by exposure to hypotonic solution, dialyzed and ultracentrifuged. The supernatant contained a substance which enhanced the activity of colony stimulating factor (CSF) in soft agar cultures of granulocyte-macrophage progenitor cells (CFU-C) from normal mouse bone marrow. The growth-enhancing effect of the erythrocyte factor was observed when mouse L-cell conditioned medium was used as the CSF source and also when serum from endotoxin-treated mice or from mice undergoing graft-versus-host reaction was used as the stimulant. The erythrocyte factor effect was also detected by 3H-thymidine uptake of bone marrow cells in liquid cultures. These results suggest that the effect of the erythrocyte factor on CSF is not restricted to CSF from a specific source nor to semi-solid agar cultures.