The maturation state of three types of granulocyte/macrophage progenitor cells from mouse bone marrow

The progenitor cells of neutrophil granulocytes and macrophages which are able to proliferate and differentiate in vitro (CFU-c) form a heterogeneous population. By the use of specific colony stimulating activities and cell separation by equilibrium density centrifugation, three subpopulations of CFU-c can be detected. These three CFU-c are characterized by buoyant densities of 1.070, 1.075 and 1.080 g.cm-3 and by their proliferative response to 18 h postendotoxin serum, colony stimulating factor from extracts of mouse embryos and uteri (CSF-pmue) and erythrocyte lysate, respectively. The three CFU-c are compared with respect to their differentiation potential, the maturation rate of their progeny cells and their proliferation capacity. It is shown that with increasing density of the CFU-c the maturation rate increases (sequential maturation of colonies derived from CFU-c with densities of 1.080, 1.075, 1.070 g.cm-3) and the proliferation capacity decreases (colony size decreases in the sequence of CFU-c with densities 1.070, 1.075, 1.080 g.cm-3). Concerning the differentiation potential it is shown that all three CFU-c detected have the capacity to form granulocytes as well as macrophages. On the basis of these results it is concluded that the CFU-c with densities of 1.070, 1.075 and 1.080 g.cm-3 represent a maturation sequence.