CD8+ T cell responses in F-MuLV infected Treg-depleted DEREG mice. F-MuLV-infected DEREG mice were treated with diphtheria toxin (DT) to deplete Foxp3+ Tregs during the first 10 days of infection (white columns). Control mice were infected but received PBS instead of DT (black columns). Flow cytometry was used to determine numbers of CD8+ T cells reactive with FV-DbgagL class I tetramers (A), or numbers of CD43+CD8+ T cells expressing granzyme A (GzmA) or granzyme B (GzmB) (B). Each column represents mean numbers plus SEM per one million nucleated cells for a group of 5-7 mice. Data was pooled from two independent experiments with similar results. Differences between the groups were analyzed by an unpaired t-test. Statistically significant differences between the groups are indicated in the figure. C. Splenocytes from naïve mice were loaded with FV-DbGagL peptides and labelled with CFSE to perform an in vivo CTL assay. As negative control, equal numbers of cells without FV peptide were used from CD45.1 B6 mice. Target cells were injected intravenously into naïve DEREG mice, DEREG mice infected for 10 days or F-MuLV-infected DEREG mice treated with DT. A histogram of CD45.1+ CFSE- (transferred cells without peptide) and CFSE+ cells (peptide loaded) from the spleen of representative mice for each group (one from a group of 5 animals) is presented. The figure shows the percentage of target cell killing in the spleen. D. Flow cytometry was used to determine the mean fluorescence intensity (MFI) of Eomesodermin (Eomes) in CD8+ T cells from naïve mice and CD8+ T cells reactive with FV-DbgagL class I tetramers from 10 days F-MuLV infected mice. Differences between the groups were analyzed by an unpaired t-test. Statistically significant differences between the groups are indicated in the figure.