[The dependence of the formation of stromal CFU-f colonies on the stimulating action of hematopoietic cells].

CFU-f-derived stromal colony formation was accomplished in adherent marrow cell cultures (AMCC) with serum-rich medium. It turned out to require additional stimulation by hemopoietic feeder cells: by irradiated marrow cells and spleen cells if they possess megakaryocytes and platelets or by platelets from the blood. PDGF, EGF and IL-3 did not substitute the colony stimulating activity of feeder cells. Thymus, lymph node cells and blood leucocytes had no colony stimulating activity. At low oxygen concentrations which improve colony formation the stimulating activity of hemopoietic feeder cells was expressed, as well. Thus, CFU-f colony formation depends on stimulation by hemopoietic cells in addition to serum growth factors. In full populations of marrow cells the CFU-f colony formation is stimulated by marrow cells which accompany the CFU-f.