Radiosensitivity of hematopoietic cells is determined by Puma gene dosages and radiation dosages. (A) Total number of LSK cells in mice (n = 3 per group). The number of surviving LSK cells in 1 pair of femurs of Puma^−/− mice was comparable with that from Puma^+/+ mice before irradiation, but this number was significantly higher in Puma^−/− than in Puma^+/+ mice at 3 days after 5 Gy TBI and was significantly higher in Puma^−/− and Puma^+/− mice than in Puma^+/+ mice at 3 days after 9 Gy TBI. **P < .01. (B) Total number of HPCs in 1 pair of mouse femurs before and after radiation. The number of HPCs (Lin⁻c-Kit⁺) in Puma^−/−, Puma^+/−, Puma^+/+ mice was similar before irradiation but is significantly higher in Puma^−/− and Puma^+/− mice than in Puma^+/+ mice at 3 days after 5 Gy TBI. There was a significantly higher number of Lin⁻c-Kit⁺ cells in Puma^−/− mice than in Puma^+/− and Puma^+/+ mice at 3 days after 9 Gy TBI (n = 3 mice per group). *P < .05, ***P < .001. (C-D) Total number of T and B lymphocytes in 1 pair of femurs of mice. There was no significant difference in cell numbers of differentiated cells in nonirradiated mice, regardless of Puma genotype. The number of surviving differentiated T cells (CD3e⁺) and B cells (B220⁺) in Puma^−/− and Puma^+/− mice was significantly greater than those in Puma^+/+ mice at 3 days after 5 Gy TBI. Three days after 9-Gy TBI, there was no difference in cell numbers of T and B cells in these mice (n = 3 per group). **P < .01. (E) Total number of myeloid cells in 1 pair of femurs of mice before and after exposure to radiation. There was no significant difference in myeloid cell numbers between Puma^−/− or Puma^+/− mice or Puma^+/+ mice (n = 3) before and after radiation (5 or 9 Gy TBI). All data are shown as mean ± SD.