Radioresistant cells and cortical epithelial cells inefficiently induce apoptosis. HY^cd4 D^bo female BM was mixed with female or male BM from WT mice and transferred into WT female and male recipients as controls. (A) A cohort of WT male mice reconstituted with a mixture of HY^cd4 D^bo female BM and nontransgenic D^bo female BM was added. Data are representative of two separate experiments. (B) A cohort of female mice expressing the K14-HYp transgene reconstituted with a mixture of HY^cd4 D^bo BM and WT female BM was added. Data are representative of five separate experiments. The frequency of active Caspase 3⁺ T3.70⁺ cells in chimeric mice is shown. Data represent the mean from three to six individuals ± SD. Fold change over the female control group is indicated. A, P = 0.0463 when comparing the male radioresistant group to the WT female group and P = 0.1191 when comparing the male radioresistant group to the WT male group; B, P = 0.0042 when comparing WT male and female groups and P = 0.0085 when comparing the WT male group to the female K14-HYp group.