[Proliferation of megakaryocytic precursor cells (CFU-M) in a micro-agar culture system].

The recently described micro-agar culture system for cloning erythropoietic progenitor cells was used to study the optimum conditions for the growth of CFU-M. In this system human mononuclear cells from normal human bone marrow were suspended in agar and incubated for 12 days. Various concentrations of phytohaemagglutinin lymphocyte conditioned medium (PHA-LCM) and prostaglandin E (PGE) were added to the liquid overlayer in the presence of 2-mercaptoethanol (2-ME) for the stimulation of CFU-M. Human AB serum was used instead of fetal calf serum (FCS) in all experiments. A sigmoidal dose-response curve, with a plateau at a concentration of 5 to 10%, was obtained by the addition of different concentrations of PHA-LCM in the presence of 10(-6)PG-E. Under optimal conditions (5% PHA-LCM, PGE 10(-6)M) a linear relation was obtained between the number of seeded cells and the megakaryocytic colonies formed. For routine morphological analysis the whole agar layer was stained using the Pappenheim method. For further characterization of CFU-M, an immunofluorescence test with rabbit antihuman factor VIII related antigen was performed on the whole agar layer.