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The effects of interferon-gamma (IFN-gamma) on a highly enriched population of granulocyte-macrophage colony-forming cells (GM-CFC) were assessed. When added with myeloid growth factors (interleukin-3 IL-3, granulocyte-macrophage colony-stimulating factor GM-CSF, or macrophage-CSF M-CSF), IFN-gamma inhibited the formation of colonies in soft agar assays. Furthermore IFN-gamma stimulated an increase in the number of macrophages present in colonies formed in the presence of IL-3. IFN-gamma also inhibited M-CSF-, GM-CSF-, or IL-3-stimulated 3H-thymidine incorporation in highly enriched GM-CFC. However, when added in the absence of hematopoietic growth factors, IFN-gamma promoted the survival of GM-CFC and had a modest stimulatory effect on DNA synthesis. The direct interaction of the IFN with GM-CFC was confirmed by showing its ability to rapidly activate the sodium/hydrogen antiport in GM-CFC, as do the mitogens GM-CSF, M-CSF, and IL-3. However, the effect of IFN-gamma on intracellular pH and DNA synthesis was transient and pretreatment with IFN markedly inhibited the ability of GM-CSF, M-CSF, and IL-3 to activate the sodium/hydrogen antiport. IFN-gamma has a dual effect on GM-CFC, decreasing the rate of cell death but also limiting the proliferative response to CSFs.
Kan et al. (Fri,) studied this question.