Effects of various treatments of CFU-S seeding efficiency in mice.

Stem cell seeding efficiency and the proportion of CFU-S in the S phase after cytosine arabinoside (Ara C) treatments were assessed. We found no difference in the "f" factor between quiescent and cycling CFU-S. A survey of the literature indicates conflicting data regarding the possible correlation between the kinetic status of CFU-S and the "f" factor, but there is no question that the "f" factor can vary with treatment of either the donor or the recipient. It seems, therefore, important to determine the "f" factor for each new treatment protocol regardless of the cycling state of the stem cells if one is interested in knowing the absolute number of CFU-S in the marrow.