Relationship between cells forming colonies in diffusion chambers in vivo (CFU-D) and cells with high proliferative potential in vitro (HPP-CFU-1 and -2)

In vivo diffusion chambers implanted in normal mice after 5 days of bone marrow cell culture contained precursor cells that in the presence of recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF), interleukin 3 (IL-3), or colony-stimulating factor 1 (CSF-1), alone or in combination, formed both small and large (high proliferative potential colony-forming cells, HPP-CFC) macrophage-containing colonies in vitro. Synergistic factor from serum-free 5637 cell-conditioned medium (SF₅₆₃₇) enhanced HPP-CFC colony growth only in cultures containing CSF-1. Higher numbers of CSF-1- plus IL-3-responsive colony-forming cells (HPP-CFC-2) were detected in diffusion chamber colony-forming unit (CFU-D) colonies than in intercolony areas, suggesting that they were derived from cells that give rise to the diffusion chamber colony. Further study demonstrated that CFU-D colonies contained cells that formed large macrophage-containing colonies (HPP-CFC-1) in CSF-1- plus SF₅₆₃₇-containing cultures. These findings suggest that single cells (CFU-D) forming colonies in diffusion chambers in mice can give rise to both HPP-CFC-1 and to cells probably respresenting their progeny, HPP-CFC-2.