T-cell defects in the absence of Ptch1. (A) Total numbers of thymocytes (mean plus SD calculated from 8 mice of each genotype). *P < .05 by one-way ANOVA. (B) Representative dot-plots of T-cell subsets. The mean percentage shown for each subset was calculated from 8 mice of each genotype. (C) Total numbers of T-cell subsets: CD4⁻CD8⁻ double negative (DN); CD4⁺CD8⁺ double positive (DP); CD4⁺ single positive (CD4); CD8⁺ single positive (CD8). Mean plus SD calculated from 8 mice of each genotype. *P < .05 by 2-tailed Mann-Whitney test. (D) Annexin V expression on DP thymocytes. The mean percentage of annexin V⁺ calculated from 3 mice for each genotype is shown.