Altered thymocyte development in CCX-CKR^−/− mice. (A) Representative dot plots showing CD4 and CD8 expression on thymocytes to assess proportions of DP (CD4⁺CD8⁺) and SP (CD4⁺CD8⁻ or CD8⁺CD4⁻). (B) Quantitation of proportions (top) and total number (bottom) of DP and SP cells. Representative dot plots and data pooled from 4 independent experiments: WT, n = 20; and CCX-CKR^−/−, n = 19. Two-tailed unpaired t test: ***P < .001. (C) Analysis of CD62L and CD69 expression to identify immature and mature CD4 SP (top) and CD8 SP (bottom) and the ratio of immature to mature CD4 SP (top) and CD8 SP (bottom). Representative dot plots and data pooled from 2 independent experiments; n = 11 per group. Two-tailed unpaired t test (immature and mature CD4 SP proportions: **P = .0013, ***P < .0001; and immature CD8 SP proportions: *P = .0425. Two-tailed unpaired t test with Welch correction (CD4 immature/mature ratio): ***P < .0001; mature CD8 SP proportions: *P = .0308. (D) Analysis of DP and SP cell localization in thymus sections stained with anti-CD4 (green) and anti-CD8 (red) of WT (left), CCX-CKR^−/− (middle), and CCR7^−/− (right). DP cells appear yellow. Representative images from one of 3 independent experiments: WT, n = 7; CCX-CKR^−/−, n = 9; and CCR7^−/−, n = 6. Scale bar represents 250 μm. (A,C) Numbers adjacent to gates indicate percent positive. (B-C) Bars represent means.