Relative HSC repopulating abilities in old CXB-12 donors.

Bone marrow cells from 4 male 24-month-old CXB-12 donors (Gpi1^a/Gpi1^a) were mixed with BMCs from young congenic CByB6F1 standard competitors (Gpi1^b) and injected into NK cell–depleted lethally irradiated CByB6F1 recipients using 4 recipients per donor, each given 4 × 10⁶ donor and 2 × 10⁶competitor BMCs. Experimental conditions, analyses, and calculations were the same as in Figure 1. “CXB1-11 young” gives the average total RUs per mouse of the CXB RI lines 1 to 11 shown in Figure 1. Total RUs per CByB6F1 competitor is 1 RU per 10⁵ BMCs multiplied by the average total BMCs ( × 10⁻⁵) per competitor mouse, assuming 2 tibias and 2 femurs contain 25% of the total bone marrow.