Representative parabiotic study. Outline of the experimental approach and results from a representative study in which ROSA26 and PeP3^b parabionts were joined for 3 weeks. After separation, the percentages of marrow granulocytes, CFU-GMs, and HSCs of PeP3^b (green) versus ROSA26 (blue) phenotype were assessed in each parabiont. To calculate the percentage of marrow granulocytes and of CFU-GMs and HSCs that were exchanged, data from the parabiotic pair were averaged as shown.