Enrichment for primitive hemopoietic progenitors of marrow cells from 5-fluorouracil-treated mice and normal mice.

Study of the mechanisms regulating stem cells would be significantly facilitated if a purified population of stem cells were available. During the last 4 years, our laboratory has been engaged in enrichment of murine marrow cells for primitive hemopoietic progenitors. We primarily used marrow cells from mice treated with 150 mg/kg of 5-fluorouracil (5-FU), and our assay for the primitive progenitors was formation of multilineage colonies supported by a combination of interleukin-3 (IL-3) and IL-6. First, we found that post-5-FU marrow cells with a density of 1.0631-1.0770 g/cm3, negative for lineage-specific markers and positive for Ly-6A/E are routinely enriched for multipotential progenitors by approximately 800-fold. We then observed that J11d.2 and c-kit are additional useful markers for further enrichment of the primitive hemopoietic progenitors. Cell cycle-dormant primitive progenitors are primarily in the J11d.2+ fraction, whereas more mature progenitors are J11d.2-. The primitive progenitors express relatively low levels of c-kit, while more mature, actively cycling progenitors express high levels of c-kit. Combinations of these markers may be useful in enrichment of marrow cells of normal mice for primitive hemopoietic progenitors.