title: Murine leukemia viruses: induction of macrophage production of granulocyte-macrophage colony-stimulating factor in vitro.
abstract: Infection in vitro of freshly explanted N:NIH(S) mouse bone marrow with ectopic murine leukemia viruses produced an increase over control uninfected cultures in the 50 or more cell granulocyte-macrophage (GM) colonies and 10-49 cell clusters detected after 7 days of incubation in 0.3% agar at 37 degrees C and 7% CO2. This effect was observed only at plating densities above 5.0 X 10(4) cells/ml and was not observed with macrophage-depleted populations of colony-forming units of GM progenitor cells (GM-CFUc) purified by isopyknic density gradient centrifugation of nonadherent cells harvested from long-term bone marrow cultures. Fewer virus-infected, compared to uninfected, peritoneal exudate macrophages were required to stimulate the same number of GM colonies and clusters in a given number of purified GM-CFUc. In contrast, murine leukemia virus infection of T-lymphocytes or NIH/3T3 embryo fibroblasts did not stimulate release of GM-CFUc coloney-stimulating factor (CSF). Single Cell suspensions of virus-infected freshly explanted whole bone marrow grown in CSF concentrated from L929 or WEHI-3 cell-conditioned medium produced more GM-CFUc colonies and GM clusters/1 X 10(5) cells compared to single cell suspensions of uninfected marrow. This phenomenon suggests that the colonoy-forming cells responding to CSF from virus-infected marrow may have been different from those responding to L929 or WEHI-3 cell CSF. The data indicate that increased granulopoiesis observed following retrovirus infection in vivo or in long-term marrow cultures was attributable in part to virus stimulation of production of CSF by adherent marrow stromal cells including macrophages.
mesh_terms: D000818:Animals; D001853:Bone Marrow / Q000276:immunology; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D003115:Colony-Stimulating Factors / Q000096:biosynthesis*; D006098:Granulocytes / Q000276:immunology*; D007739:L Cells; D009052:Leukemia Virus, Murine / Q000276:immunology*; D008264:Macrophages / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008819:Mice, Nude; D014412:Tumor Virus Infections / Q000276:immunology*
chemical_list: D003115:Colony-Stimulating Factors