TBI selectively suppresses LKS⁺-cell replicative and clonogenic function. (A-F) Mice were exposed to 6.5 Gy TBI or not irradiated as control (CTL). At 28 days after TBI, BM-MNCs were isolated from irradiated and control mice. The clonogenic function of HPCs and HSCs was measured by CFC assay and day-35 CAFC assay, respectively. The frequencies of LKS^- and LKS⁺ cells in BM-MNCs were quantified by flow cytometry (B,E). The number of various CFUs and day-35 CAFCs is expressed as a function of BM-MNCs (A,D) or as a function of LKS^- and LKS⁺ cells, respectively (C,F). The data are presented as mean ± SE (n = 5 for CFC assay and n = 3 for CAFC assay). (G-H) At 28 days after TBI, BM-MNCs were isolated from irradiated and control mice and single LKS⁺ cells were sorted into wells of rounded-bottom plates. After 14 days of culture with SCF/TPO, wells with a single seeded cell that had undergone at least one round of cell division were scored and graded by the number of cells produced. The results are presented as a percentage of LKS⁺ cells that divided (G). Similarly, single sorted cells were cultured with SCF/TPO/IL-3 for 14 days and the formation of hematopoietic-cell colonies (> 50 cells) was scored based on the size of the colonies. The data are expressed as a percentage of LKS⁺ cells that formed colony (H). ^*P < .05 and ^***P < .001, compared with control.