Presence of colony-promoting activity-responsive cells as a separate compartment of granulocytic cell lineage in mice.

A population of cells that responds to colony-enhancing factor has been reported to constitute the most immature subpopulation in the compartment of granulocyte/macrophage progenitors (GM-CFC). A similar colony-promoting activity (CPA) was found in the supernatant of long-term cultures of murine bone marrow cells. Here, some characteristics of the cells responsive to CPA were studied. The CPA-responsive cells in the spleen and bone marrow of W/WV mice were as numerous as in +/+ litter-mates. The concentration of CPA-responsive cells was independent of those of other cell populations, namely pluripotent stem cells (CFU-S), pluripotent precursor cells in vitro and GM-CFC in the spleen and bone marrow. Seeding efficiency in the spleen of irradiated mice and the cell-cycle state of CPA-responsive cells also differed from those of CFU-S and GM-CFC. Accordingly, the target of CPA appears to constitute a separate compartment in the progenitor populations of granulocytic lineage.