Physical and kinetic properties of haemopoietic progenitor cell populations from mouse marrow detected in five different assay systems.

Properties of haemopoietic progenitor cells detected in several different assays have been compared in order to position them within the haemopoietic developmental lineage. The spleen colony-forming cell (CFUs), the high proliferation potential colony-forming cell (HPP-CFC) and two granulocyte-macrophage colony-forming cells (GM-CFC-1 and GM-CFC-2) have been studied. Two experimental techniques were used: separation of cells on the basis of their buoyant density and comparison of the survival of haemopoietic cells after donor mice had been injected with the cytotoxic drug 5-fluorouracil (5-FU). On linear BSA gradients the modal buoyant densities of CFUs, HPP-CFC and GM-CFC-1 were the same, 1.070 g cm-3; the density of GM-CFC-2 was higher, 1.075 g cm-3. GM-CFC-2 colonies were much smaller and contained far fewer cells than HPP-CFC or GM-CFC-1 colonies, even after prolonged culture, and this suggests that dense haemopoietic progenitors have less proliferation potential. This was confirmed by comparison of the size of colony formed, under identical culture conditions, by progenitors of different densities. Mean colony diameter was inversely related to the density of the progenitor cell. With the exception of GM-CFC-1, low density progenitors were more resistant to the cytotoxic effects of 5-FU than high density precursor cells (GM-CFC-2). Consequently, the GM-CFC-1 could be distinguished from GM-CFC-2 on the basis of buoyant density and from the other low density populations on the basis of post-FU kinetics. The reasons why the GM-CFC-1 should be more sensitive to 5-FU than other low density progenitors are discussed and the relation of these low density precursors to one another in terms of their position within the haemopoietic developmental lineage is elucidated.