DETERMINATION OF DIFFERENTIATION OF BIPOTENT HEMATOPOIETIC PROGENITOR CELLS INVITRO

Murine bone marrow cells fractionated in a discontinuous density gradient of Ficoll-Metrizoate solution produced a fraction with more than 90% colony-forming efficiency. When this fraction was seeded in untreated CM from the abdominal wall, it produced neutrophil (66%), macrophage (25%), mixed type (7%) and blast cell (2%) colonies. When CM was used after trypsinization to inactivate the granulocyte stimulating activity, most of colonies found (93%) were macrophage which kept the number of colonies unchanged. Thus, we concluded that about 40% of the cells in the fraction were able to differentiate to both macrophages or neutrophils and that the direction of differentiation was controlled by humoral factors present in the culture medium. © 1979.