TBI causes sustained quantitative reduction of MPPs but not of HPCs and HSCs. C57BL/6 mice were exposed to a sublethal dose (6 Gy) of TBI or were sham irradiated as a control (CTL). Two months after TBI, BM cells (BMCs) were harvested from the 2 hind legs of individual mice for analysis. (A) Representative gating strategy of flow cytometric analysis for HPCs (Lin^–Sca1^–c-kit⁺ cells), LSK cells (Lin^–Sca1⁺c-kit⁺ cells), MPPs (CD150^–CD48^–LSK cells), HSCs (CD150⁺CD48^–LSK cells), ST-HSCs (CD34⁺CD150⁺CD48^–LSK cells), and LT-HSCs (CD34^–CD150⁺CD48^–LSK cells) in lineage-negative (Lin^–) BM-MNCs is shown. (B) Frequencies (upper panel) and total numbers (lower panel) of HPCs, LSK cells, MPPs, HSCs, ST-HSCs, and LT-HSCs in BMCs from each mouse are presented as mean ± SD (n = 6-8 mice/group). *P < .05, **P < .01, and ***P < .001, TBI vs CTL.