Limiting-dilution transplantation of 500 LT-HSCs (but not 30 HSCs) from old wild-type and p53 mutant mice results in differential white blood cell reconstitution in lethally irradiated recipients. LT-HSCs were isolated from CD45.2 donor mice based on their status as lin^−/lo, Sca-1⁺, c-kit⁺, Flk-2⁻. Either 30 or 500 LT-HSCs from CD45.2 test mice were injected into marrow-ablated CD45.1 recipients. Recipient mice were analyzed 4, 8, 12, and 24 weeks after transplantation to assess the percentage of peripheral white blood cells produced from transplanted CD45.2 LT-HSCs. These experiments were performed in duplicate. For each experiment, 3 old donor mice of the same genotype were used, donor cells were pooled, and HSCs were isolated and injected into 6 irradiated recipient mice. Error bars indicate standard error of the mean.