DC precursors in the BM and their dependence on IL-7 signals. (A) Hematopoietic precursor cells in the bone marrow were analyzed by flow cytometry and identified as follows: HSCs (Lin⁻ Sca-1⁺ c-Kit⁺), myeloid progenitors (MPs; Lin⁻ Sca-1⁻ c-Kit⁺; including CMPs, GMPs, and MEPs), CLPs (Lin⁻ Sca-1^low c-Kit^low IL-7Rα⁺) and CDPs (Lin⁻ c-Kit^int M-CSFR⁺ Flt3⁺). (B,C) Precursor cells isolated from the BM of IL-7^tg (B) and IL-7Rα ^−/− (C) mice were analyzed by flow cytometry. Cell numbers (± SD) are shown as a percentage of control mice (n = 3). (D) Ratio of WT (CD45.1⁺) versus IL-7Rα ^−/− (CD45.2⁺) BM-derived cells in mixed BM chimeras (host: CD45.1/2⁺) is shown for BM HSCs, MPs, CDPs, and CLP-enriched cells (Lin⁻ Sca-1^low c-Kit^low cells containing 50%-70% CLPs), as well as BM granulocytes (Gran.; n = 3-5). Differences in reconstitution efficiencies between experiments were normalized by adjusting the ratio of IL-7Rα^−/− and WT HSCs in the BM to 1. Statistical significance is calculated relative to BM HSCs (*P < .05; **P < .01).