Some Factors Influencing Granulocytic Colony Formation In Vitro by

The experiments presented in this paper are essential for CSA production but docu-were designed to characterize the colony- mont the importance of neutrophilic gran-stimulating activity (CSA) from white ulocytes to enhance colony formation. blood cell feeder layers on colony forma- Possible differences between colony en-tion by peripheral blood CFCs in soft agar hancement by granulocytes and red cell double-layer cultures. The data confirm hemolysate are discussed. earlier observations that mononuclear cells G RANULOCYTIC PROGENITOR cells (in vitro colony-forming cells, CFC) can be detected by their ability to form discrete colonies in semi-solid culture medium provided a factor is present to initiate and sustain colony growth (colony-stimulating activity, CSA). ’ Using murine hemopoietic cells as a source of CFC, a variety of tissues as well as urine and serum from a number of mammalian species, including man, have been shown to contain colony-stimulating activity.2 However, with human hemopoietic cells, no CSA has been observed with the majority of these materials. Colony-stimulating activity for human hemopoietic cell cultures has been demonstrated with white blood cells (WBC), used either as feeder layers or to condition medium.5’6 Although no final conclusion is yet possible as to which leukocyte generates CSA, evi-dence is accumulating to indicate that the peripheral blood monocyte con-tributes to colony stimulation in vitrb. These data were obtained using un-fractionated human bone marrow cells as a source of CFC.7 However, because of the heterogeneity of cells in the marrow, this source of cells for culture probably does not represent the ideal target, and we have used peripheral white blood cells as a source of CFC. The purpose of the present experiments was to compare unfractionated leukocytes with mononuclear cells (MNC) obtained using Isopaque-Ficoll gradients in order to determine both the CFC content and colony-stimulating activity of blood cell populations