Interleukin 1 plus interleukin 3 plus colony-stimulating factor 1 are essential for clonal proliferation of primitive myeloid bone marrow cells

The clonal growth in nutrient agar at low cell densities of high-proliferative potential colony-forming cells (HPP-CFC) of bone marrow obtained from mice treated 2 days earlier with 5-fluorouracil (FU) (FU(2d)BM) has been shown to require a combination of three growth factors, interleukin 1 (IL-1), interleukin 3 (IL-3), and macrophage colony-stimulating factor (CSF-1). These HPP-CFC have been enriched 140-fold from FU(2d)BM by fluorescence-activated cell sorting of 7/4-, B220-, and L₃T₄-negative cells. The mean of the plating efficiencies of these enriched populations was 4.4% and no growth was observed when the factors were used singly. Similarly, enrichments of 16-fold were obtained from FU(2d)BM using immunomagnetic Dynabeads with anti-7/4 plus anti-B220 (meaning plating efficiency 0.5%). The further additions of human granulocyte CSF or mouse granulocyte-macrophage CSF or both to IL-1 plus IL-3 plus CSF-1 did not increase HPP-CFC colony formation, but both augmented the small colony formation with IL-1 plus IL-3, IL-3 plus CSF-1, or IL-1 plus CSF-1.