Thymic granulocyte development is IL-7Rαdependent. (A) The development of CD45.2⁺ ETPs and thymic granulocytes in the absence of IL-7Rα was examined in competitive BM chimeras 8 weeks after reconstitution of lethally irradiated CD45.1⁺ hosts. (B) The development of CD45.2⁺ BM Lin⁻Sca1⁺Kit⁺ (LSK) and splenic granulocytes in the absence of IL-7Rα was examined in mixed BM chimeras 8 weeks after reconstitution of lethally irradiated CD45.1⁺ hosts. (C) Shown is the mean percent CD45.2⁺ donor contribution to BM LSK, splenic granulocytes, ETPs, or thymic granulocytes by IL-7Rα^+/+ (black bars) or IL-7Rα^−/− (gray bars) BM. Three mice per group were examined. Error bars represent SEM. ***P < .001 for the CD45.2⁺ donor chimerism of the indicated population compared with BM LSK CD45.2⁺ donor chimerism.