Reduced frequencies of ETP in the steady thymus of CCR7^−/−CCR9^−/− mice. Thymocytes from wild-type (wt), CCR7^−/−, CCR9^−/−, and CCR7^−/−CCR9^−/− (DKO) mice were stained with antibodies against lineage markers, CD4, CD8, CD25, CD44, and CD117 and analyzed by flow cytometry. (A) Analysis of early T-lineage progenitor (ETP; Lin⁻CD25⁻CD44⁺CD117^hi). (B) Analysis of DN2 (Lin⁻CD25⁺CD44⁺CD117⁺) and DN3 (Lin⁻CD25⁺CD44⁻CD117^−/lo) compartments. (C) Analysis of double-negative (DN), double-positive (DP), and single-positive (SP) populations. Numbers in quadrants and adjacent to gates represent frequencies of viable thymocytes. (D) Statistical analysis of flow cytometric results from multiple individual mice (wt: n = 36, CCR7^−/−: n = 8, CCR9^−/−: n = 3, DKO: n = 12). Data represent mean ± SEM.