Two distinct
bone marrow-derived blast
colony-forming cells can generate colonies of lineage-restricted
progenitor cells in
agar cultures of murine
bone marrow. Both cell types selectively had a Kit(+) ScaI(+)
phenotype distinguishing them from most lineage-restricted
progenitor cells. Multicentric blast
colony-forming cells stimulated by
stem cell factor plus interleukin-6 (IL-6) (BL-CFC-S) were separable from most dispersed blast
colony-forming cells stimulated by Flt3 ligand and IL-6 (BL-CFC-F) using
CD34 and Flt3R probes. Multicentric BL-CFC-S cofractionated with
colony-forming units,
spleen (CFU-S) supporting the possibility that the 2 cells may be identical. The colony populations generated by BL-CFC-S were similar in their
phenotype and proliferative capacity to
progenitor cells in whole
bone marrow but the progeny of BL-CFC-F were
skewed with an abnormally high proportion of Kit(-) Flt3R(+) cells whose clonogenic cells tended to generate only
macrophage progeny. Both blast colony populations had a high percentage of GR1(+) and Mac1(+) cells but BL-CFC-F colonies also contained a significant population of
B220(+) and IL-7R(+) cells relevant to the superior ability of BL-CFC-F colony cells to generate
B lymphocytes and the known dependency of this process on Flt3 ligand and IL-7. The commitment events and
phenotypic changes during the generation of differing
progenitor cells in blast colonies can now be clonally analyzed in a convenient in vitro culture system.
