Expression of the macrophage-specific colony-stimulating factor in human monocytes treated with granulocyte-macrophage colony-stimulating factor

The macrophage-specific colony-stimulating factor (CSF-1, M-CSF) regulates the survival, growth and differentiation of monocytes. We have recently demonstrated that phorbol ester induces expression of CSF- 1 in human monocytes. These findings suggested that activated monocytes are capable of producing their own lineage-specific CSF. The present studies demonstrate that the granulocyte-macrophage colony-stimulating factor (GM-CSF) also induces CSF-1 transcripts in monocytes. Furthermore, we demonstrate that the detection of CSF-1 RNA in GM-CSF- treated monocytes is associated with synthesis of the CSF-1 gene product. The results thus suggest that GM-CSF may indirectly control specific monocyte functions through the regulation of CSF-1 production. These findings indicate another level of interaction between T cells and monocytes.