Action of granulopoiesis-stimulating cytokines rhG-CSF, rhGM-CSF, and rmGM-CSF on murine haematopoietic progenitor cells for granulocytes and macrophages (GM-CFC)

The aim of this study was to provide new data to the knowledge of mechanisms by which recombinant human granulocyte colony-stimulating factor (rhG-CSF), recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) and recombinant murine granulocyte-macrophage colony-stimulating factor (rmGM-CSF) enhance the numbers of colonies growing from hematopoietic progenitor cells for granulocytes and macrophages (GM-CFC) in the murine bone marrow. The in vitro technique for cultivating GM-CFC from normal bone marrow cells was used. For evaluation of stimulatory actions of the drugs studied, the factors themselves or sera of mice given these factors were added to the cultures. The factors or the sera were present in the cultures either as the only potentially stimulatory agents or acted jointly with a suboptimum concentration of recombinant murine interleukin-3 (rmIL-3). It was found that both rhG-CSF and rmGM-CSF stimulate the proliferation of GM-CFC by a combination of direct mechanisms (direct actions on the target cells) and indirect effects (effects mediated through the induction of other cytokines and/or growth factors in the murine organism). The rhGM-CSF exhibited somewhat weaker in vitro effects in comparison with the other two factors and only indirect effects were noted. Additional in vivo experiments documented that, in spite of differences in mechanisms of action of the individual drugs studied on murine bone marrow cells in vitro, equal in vivo doses of the factors induce quantitatively similar effects on the production of GM-CFC in vivo.