EFFECTS OF STEM-CELL FACTOR (SCF) ON HUMAN MARROW NEUTROPHIL, NEUTROPHIL MACROPHAGE MIXED, MACROPHAGE AND EOSINOPHIL PROGENITOR-CELL GROWTH

The effects of stem cell factor (SCF) on the subpopulations of granulocyte/macrophage colony-forming units (CFUGM) were examined. Hematopoietic progenitor cells were enriched from normal adult bone marrow specimens by immunomagnetic beads using an anti-CD34 antibody and lineage marker antibodies for positive selection and negative selection, respectively. SCF enabled neutrophil and neutrophil/macrophage mixed progenitors to respond to granulocyte/macrophage colony-stimulating factor (GM-CSF) or interleukin 3 (IL-3) and to develop the colony and further cluster formation. The neutrophil colonies stimulated by GM-CSF or IL-3 consisted mainly of immature cells, while the colonies stimulated by granulocyte colony-stimulating factor (G-CSF) consisted of mature neutrophils irrespective of the addition of SCF. In macrophage and eosinophil lineages, SCF augmented the colony formation in the presence of GM-CSF or IL-3, whereas the enhancement of total progenitor cell growth (colonies plus clusters) was not so marked as compared with the neutrophil lineage. Time-course observation revealed that SCF could stimulate macrophage and eosinophil progenitors to form colonies rapidly. These findings indicate that SCF acts on late myeloid progenitor cells in manners different from the lineages of commitment.