A kinetic study of the genetic control of hemopoietic progenitor cells assayed in culture and In vivo

The kinetics of growth of bone marrow cells from normal or genetically anemic mice ( Sl / Sl d and W / W v ) were studied in irradiated normal and genetically anemic hosts. The parameters followed included total cellularity, the number of peroxidase positive cells, and the number of cells capable of forming colonies in vivo (CFU‐S) or in culture (CFU‐C). The results of these experiments demonstrate that W and Sl defects alter the growth of CFU‐C and peroxidase‐positive cells to a modest degree; that the defects are more obvious when studied in spleen rather than in bone marrow; and that there is no additivity of W and Sl defects. Nineteen irradiated recipients of marrow from W / W v mice were studied after three to six months. Of these, 18 showed host‐type erythrocytes, while in one mouse the erythrocytes had the size distribution of W / W v cells. This finding indicated that occasionally genetically defective stem cells may repopulate irradiated hosts.