FIGURE 2.

Number of available, functional TSP niches does not decline with age. (a) Schematic of the multicongenic barcoding experiment to quantify available niches in mice of different ages. Lin⁻Flk2⁺CD27⁺ BM progenitors were isolated from eight different congenic strains (Figure S2B), mixed at equal ratios and i.v. injected into non‐irradiated 1MO, 3MO, 6MO, and 12MO mice. After 21 days, the thymi from recipient mice were analyzed by flow cytometry to quantify the number of detectable donor strains that underwent T‐cell differentiation. (b) Pie charts illustrate the number and relative frequency of distinct color‐coded donor strains in individual recipients of the indicated ages. (c) The estimated number of available functional niches in each age recipient as determined by multinomial sampling. Symbols indicate data from individual mice; bars represent means ± SEM compiled from four independent experiments (n = 10–12 mice per recipient age).