Figure 5. Cell cycle entry of different thymocyte populations. Thymocytes were stained with the corresponding antibodies to identify CD4^-/CD8^- (DN), CD4⁺/CD8⁺ (DP), CD4⁺/CD8^- (SP4) and CD4^-/CD8⁺ (SP8) cells and with an anti-Ki67 antibody to analyze cell cycle entry. A) The total percentages of cells and the percentages of Ki67⁺ cells in the different populations are shown in 3-d old (white bars) and adult (black bars) mice of both genotypes . B) Comparative analysis of Ki67 expression in the different populations between Vav1^−/− and wild-type mice. Data represent the mean percentages ± SEM of three independent experiments with n = 3 mice per group. Data were evaluated using Student’s t-test: * p < 0.05; **p < 0.01; ***p < 0.001.