Human G-CSF produced by adherent cells in the presence of human recombinant GM-CSF

Adherent cells (AdCs) in blood from normal volunteers produced granulocyte-macrophage (GM) colony-stimulating activity (CSA) in the presence of 10 ng/ml of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) in vitro. GM-CSA produced by adherent cells in the presence of GM-CSF reached a plateau level on day 6. Colonies stimulated by adherent cell-conditioned medium (AdC-CM-GM-CSF), which had been harvested after 6 days of incubation of AdCs with rhGM-CSF, were granulocyte predominant. When phagocyte-depleted marrow mononuclear cells (PD-M-MNCs) were cultured with AdC-CM-GM-CSF and anti-rabbit serum against rhGM-CSF, 99% of the colonies on day 7 were exclusively composed of neutrophils. When 2 X 10(4) PD-M-MNCs were cultured in a medium containing AdC-CM-GM-CSF, AdC-CM-GM-CSF + anti-GM-CSF, AdC-CM-GM-CSF + anti-G-CSF, or AdC-CM-GM-CSF + both of the anti-bodies, the PD-M-MNCs formed (mean +/- SD) 100 +/- 2.0%, 64.3 +/- 2.5%, 38.6 +/- 0.4%, and 6.0 +/- 0.4% GM colonies, respectively. Furthermore, northern blot analysis revealed that AdCs incubated with 10 ng/ml of rhGM-CSF for 6 h expressed much more mRNA of G-CSF than those without the CSF. These data indicated that AdCs in blood produce G-CSF in the presence of GM-CSF.