The effects of an inhibiting factor (interferon) on the in vitro growth of granulocyte-macrophage colonies.

Incorporation of preparations of mouse interferon in stimulated cultures of normal mouse bone marrow results in a decrease in the number of colonies developing, and in the appearance of unusual cells in colonies. These unusual cells have the granular, vacuolated cytoplasm of the macrophage, but lobed nuclei more typical of cells of the granulocytic series. The evidence suggests that interferon inhibits the normal multiplication and differentiation of mouse granulocyte-macrophage precursors .