CD8⁺ T-cell responses in Foxp3⁺ Treg-depleted DEREG mice. (A-C) FV-infected DEREG mice were treated with DT to deplete Foxp3⁺ Treg during the first 10 days of infection (■). Control mice were FV infected, but received PBS instead of DT (□). Flow cytometry was used to determine the absolute numbers of CD43⁺ effector CD8⁺ T cells reactive with D^bgagL class I tetramers (A), or granzyme B (GzmB; B), or the percentage of cells expressing the degranulation marker CD107a (C) in lymph nodes, spleen, and bone marrow at the peak of the FV-specific CD8⁺ T-cell response (10 dpi). Each column represents mean numbers + SEM per 1 million nucleated cells for a group of 5 to 7 mice. Data were pooled from 2 independent experiments with similar results. Differences between the groups were analyzed by the unpaired Student t test. Statistically significant differences between the groups are indicated in the figure. (D) Splenocytes from naive mice were loaded with D^bGagL peptide and labeled with CFSE. Target cells were injected intravenously into naive mice, DEREG mice infected for 10 days, and in 10-day FV-infected DEREG mice that were treated with DT. The figure shows the percentage of target cell killing in lymph nodes, spleen, and bone marrow. Each dot represents an individual mouse. Two independent experiments with similar results were performed. Differences between nondepleted and Treg-depleted groups were analyzed by the unpaired Student t test. Statistically significant differences between the groups are indicated in the figure. (E) Granzyme expression by effector CD8⁺ CD43⁺ T cells from the bone marrow of FV-infected Treg-depleted and nondepleted DEREG mice is shown at 15 dpi. The mean percentages of CD8⁺ T cells that were positive for granzyme A or granzyme B are given in the top right quadrants. A representative mouse from a group of 6 animals is shown. The experiment was repeated twice with similar results.