Isolation of a colony-stimulating factor produced by L 1210 murine leukemia cells.

Murine L1210 leukemia cells spontaneously produce very low amounts of colony stimulating factor (CSF). CSF production was markedly increased by stimulating L1210 cells with lipopolysaccharide, lectins, and sheep red blood cells. From the conditioned medium of phytohemagglutinin-stimulated L1210 cells we isolated a CSF with an apparent molecular weight of approximately 27,000. This CSF promoted the proliferation and the differentiation of murine GM-CFU showing a weak differentiation-inducing activity on WEHI-3 D (+) cells.