CCR4 is required for negative selection of OT-II thymocytes to an endogenous antigen, but not to the model TRA RIP-OVA^hi. (A) Experimental schematic for transplantation of Ccr4^+/+ or Ccr4^−/− OT-II bone marrow into OVA- or RIP-OVA^hi recipient mice. Thymi were analyzed by flow cytometry 6 wk after transplantation. (B) Representative CD4 versus CD8 flow cytometry plots from the indicated chimeric mice. (C) Cellularity of indicated thymocyte subsets from recipient mice. Means + SEM from three independent experiments, with nine mice total per group. Two-way ANOVA was used to determine if cellularity at the indicated stages was significantly affected by CCR4, OVA, or the interaction of these two factors. (D) Plots display the percentage of thymocytes deleted by the OVA TRA, calculated as the percent decrease in cellularity between OVA⁻ and RIP-OVA^hi recipients for the indicated subsets and genotypes from data in C. No significance was observed based on unpaired Student’s t tests.