Properties of Hematopoietic Progenitor Cells

Assay of hematopoietic progenitor cells has been carried out with the use of quantitative diffusion chamber culturing. Some progenitor cell properties were investigated. Hydroxyurea, which kills the fraction of normal mouse bone marrow progenitor cells synthesizing DNA, was given to donor mice of different ages. This DNA‐S fraction of progenitor cells was found to be as large as or larger than the corresponding fraction of spleen colony‐forming cells. It was concluded that the progenitor cells for the formation of granulocytes in the chambers are probably mixtures of cells which can give rise to spleen colonies and of cells able to form agar colonies. In chamber cultures, formation of granulocytes and macrophages is prominent, whereas erythropoiesis is scant or absent. This differentiation pattern was not changed by adding erythropoietin to the culture inocula. Nor did admixture of antigens to the cell inocula influence the formation of granulocytes and macrophages. The chamber progenitor cell population as a whole was found to have a near average adhesiveness to glass and fibrin, when compared with normal bone marrow cells or blood leucocytes.