Recombinant murine granulocyte‐macrophage (GM) colony‐stimulating factor supports formation of GM and multipotential blast cell colonies in culture: Comparison with the effects of interleukin‐3

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Abstract
We studied the effects of murine recombinant granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) on murine hemopoiesis in methylcellulose culture. The GM‐CSF was purified from cultures of Saccharomyces cerevisiae transfected with a cloned murine GM‐CSF cDNA. In cultures of spleen cells from normal mice, only granulocyte‐macrophage (GM) colonies were supported by GM‐CSF. Blast cell colonies were the predominant type in cultures of spleen cells from 5‐fluorouracil (5‐FU)‐treated mice. Dose‐response studies revealed that maximal GM and blast cell colony formation is achieved with 100 U/ml GM‐CSF. Blast cell colonies revealed variable but high replating efficiencies, and the secondary colonies included multilineage colonies. Serial replating of washed blast cell colonies in cultures with GM‐CSF provided evidence for the direct effects of GM‐CSF on the proliferation of multipotential blast cells. A combination of GM‐CSF and interleukin‐3 (IL‐3) did not increase the number of blast cell colonies over the level supported by IL‐3. This observation indicates that the progenitors for blast cell colonies that responded to GM‐CSF are a subpopulation of multipotential progenitors that are supported by IL‐3. Cytological studies of colonies derived from GM‐CSF and/or IL‐3 suggest that the eosinophilopoietic ability of murine GM‐CSF is less than that of IL‐3.