Fig. 5.

Enhanced levels of thymic apoptosis result in larger tTreg populations in adult thymus. (A and B) Mixed bone marrow chimeras were made in DO11.10xRag^−/− with 75% DO11.10xRag^−/− and 25% BALB/c bone marrow. Sixteen days later chimeras received either PBS or 2 mg OVA i.p. At 3 wk thymi were harvested from mice and tTreg frequencies were examined in CD4⁺ SP thymocytes of the BALB/c compartment. (A) Plots showing frequency of CD25⁺Foxp3⁺ thymocytes in CD4⁺SP BALB/c polyclonal thymocytes. (B) Bar graph showing frequency of CD25⁺Foxp3⁺ cells in CD4⁺SP BALB/c thymocytes. Data represent two experiments with four to five mice per group. (C and D) DO11.10xRag^−/− mice received 0.02 mg OVA i.p. ± low dose γ-irradiation (50 rad), and CD25⁺Foxp3⁺ thymocytes were examined 5 d later. (C) Representative FACS plots gated on CD4⁺ SP thymocytes. (D) Bar graph showing frequency of CD4⁺CD25⁺Foxp3⁺ thymocytes. Data represent three experiments. Error bars represent mean ± SEM. *P < 0.05 (unpaired two-tailed Student t test).