Proportion of the different hematopoietic lineages of donor marrow origin as determined using FISH 6 weeks posttransplant from control animals that received an equivalent marrow transplant and no HU () or mice that received HU 12 hours posttransplant (▧). Values are the mean ± SEM for two to three individual animals (except for the B220 control group, which only had 1 sample). *Significantly different v control (P < .1).