Production of colony stimulating factor by EL-4 lymphoma cells stimulated with phytohemoagglutinin.

Murine EL-4 lymphoma cells when stimulated with optimal doses of phytohemoagglutinin (PHA) release colony stimulating factor (CSF) in the conditioned medium. CSF production depends on PHA and stops when the lectin is withdrawn. The production is dependent on protein synthesis and is not related with DNA replication. The CSF produced by El-4 cells stimulates murine bone marrow cells to differentiate in vitro into mature granulocytes. Unstimulated EL-4 cells do not produce CSF while its conditioned medium is able to inhibit EL-4 proliferation in vitro. Gel filtration chromatography of conditioned medium from PHA-stimulated EL4 cells yields a peak of activity corresponding to an apparent molecular weight of 20,000-25,000 daltons.