Thymic granulocytes are reduced in the absence of thymic settling by T-cell progenitors. (A) The development of CD45.2⁺ thymic ETPs, granulocytes, and cDCs in the absence of both CCR7 and CCR9 was examined in competitive BM chimeras 8-10 weeks after reconstitution of lethally irradiated CD45.1⁺ hosts. (B) Shown is the mean CD45.2⁺ donor contribution of CCR7/CCR9^+/+ (black bars) or CCR7/CCR9^−/− (gray bars) BM to thymic ETPs, granulocytes, and cDCs. Eight animals per group were examined in 3 independent experiments. Error bars represent SEM. ***P < .001 for the CD45.2⁺ donor chimerism of the indicated population compared with BM Lin⁻Sca1⁺Kit⁺ (LSK) CD45.2⁺ donor chimerism. (C) The development of CD45.2⁺ BM LSK and splenic granulocytes and cDC in the absence of both CCR7 and CCR9 was examined in competitive BM chimeras 8-10 weeks after reconstitution of lethally irradiated CD45.1⁺ hosts. (D) Shown is the mean CD45.2⁺ donor contribution by CCR7/CCR9^+/+ (black bars) or CCR7/CCR9^−/− (gray bars) donor BM to BM LSK, splenic granulocytes, and cDC populations. Eight animals per group were examined in 3 independent experiments. Error bars represent SEM.