Different Classes of Granulocyte Progenitor Cells Expressed in In Vivo Plasma Clot Diffusion Chamber Cultures

Preliminary data suggest that at least two classes of granulocyte progenitor cells may be distinguished in the in vivo plasma clot diffusion chamber culture system. Based on several criteria, progenitor cells giving rise to granulocyte colonies on day 4 of culture (CFU-D4) appear to be different from those giving rise to colonies on day 7 (CFU-D7). These criteria include differences in the cycling characteristics of these progenitor cells as measured with cytosine arabinoside, in their resistance to osmotic lysis, in their size as determined by velocity sedimentation, and in their morphological development. The results suggest that the CFU-D7 represents an earlier progenitor cell than the CFU-D4 in the differentiation pathway of the granulocyte which in some respects displays behavior similar to that of the CFU-S.