Development of spleen CFU-S colonies from day 8 to day 11: relationship to self-renewal capacity.

To investigate the persistence of spleen colonies from day 8 to day 11 of their development, we injected low numbers of marrow cells in order to obtain single colonies on the spleens of irradiated mice. Colonies were isolated on either half of the spleen on the eighth day. The position of day-11 colonies, determined relative to the ligature, indicated where novel colonies appear between those times. The results showed no evidence of the persistence of colonies from day 8 to day 11. The self-reproduction capacity of CFU-S that survive various cytotoxic drugs depends on the specific subpopulations that are affected by the drug. Using cyclophosphamide, busulphan, or BCNU, the self-renewal capacity of surviving CFU-S was manipulated. The results show that after cytotoxic treatments, a high day-11-day-8 ratio is not necessarily a reflection of a high self-renewal capacity of the CFU-S population that forms the day-11 colonies.