Quantitative measurements of HSCs and HPCs with or without 4-Gy irradiation. (A) Quantitative analysis of the frequencies of LT-HSCs, ST-HSCs plus multipotent progenitors (CD34⁺LKS) and HPCs (LKS⁻) in the Puma^+/+ and Puma^−/− mice without irradiation by flow cytometry. The percentage of each cell population (top) was calculated by the acquired number of the each population divided by the acquired number of CD45⁺ nucleated cells. The absolute number per harvest (bottom) was calculated by percentage of the cells multiplied by the number of BMNCs. The Student t test was used for the statistical analysis between groups (n = 7). (B) Relative increase of LKS cells after TBI in the absence of Puma. The Puma^+/+ and Puma^−/− mice (n = 3 in each phenotype) were subjected to 4-Gy irradiation (IR). LKS cells were measured in the bone marrow of the mice 6 hours after radiation in comparison with the nonirradiated (NR) controls (n = 3 in each phenotype). Representative profiles in flow cytometry from NR (left) and IR (right) groups were shown. (C) The percentage of LKS cells in the bone marrow (left) and the absolute number per harvest (right) with and without radiation were summarized (*P < .05).