title: Factors influencing in vitro production of colony-stimulating factor by mononuclear leukocytes from humans.
abstract: The purpose of this study was to identify factors that influence the production of colony-stimulating factor by leukocytes of humans. The use of nonadherent light-density bone marrow cells is semisolid agar cultures to assay the concentrations of colony-stimulating factor in the supernatant of monocyte and mononuclear leukocyte cultures made it possible to distinguish between colony-stimulating factor, which stimulates colony-forming cells directly, and monocyte-dependent stimulating activity, which acts indirectly, by increasing the monocyte production of colony-stimulating factor. Colony-stimulating factor was not detectable in the cytosol of monocytes; that detected in culture must, therefore, have been newly synthesized. Synthesis was enhanced independently by heat-inactivated human serum and by semipurified serum fractions enriched with monocyte-dependent stimulating activity. The kinetics of the production of colony-stimulating factor in the presence and absence of monocyte-dependent stimulating activity indicated that the latter facilitated monocyte production of the former. Factors released from neutrophils were shown to reduce the production of colony-stimulating factor and thr proliferation of colony-forming cells and thus may provide a feedback control mechanism limiting the proliferation of neutrophils.
mesh_terms: D003115:Colony-Stimulating Factors / Q000096:biosynthesis*; D003470:Culture Media; D006801:Humans; D007962:Leukocytes / Q000378:metabolism*; D009504:Neutrophils / Q000378:metabolism; D013997:Time Factors
chemical_list: D003115:Colony-Stimulating Factors; D003470:Culture Media