Figure 3. Functional properties of activated PD-1^hi and PD-1^lo CD8⁺ T cells during acute FV infection.

C57BL/6 mice were infected with FV and CD8⁺ T cells were harvested at 10 dpi.

Multi-parameter flow cytometry was used to compare activated (CD43⁺) PD-1^hi and PD-1^lo CD8⁺ T cells for intracellular production of the cytokines IFNγ, TNFα, and IL-2 and the production of granzymes or the expression of the degranulation marker CD107a. A. Mean percentages plus SEM of CD43⁺ CD8⁺ T cells producing IFNγ, TNFα, or IL-2 are shown. B. Mean percentages plus SEM of individual CD43⁺ CD8⁺ T cells producing no, 1, 2, or 3 different cytokines at the same time. The figure shows PD-1^hi (left) versus PD-1^lo (right) cells using data pooled from two independent experiments (n=8) with similar results. C. Mean percentages plus SEM of activated PD-1^hi and PD-1^lo CD8⁺ T cells expressing granzyme A, granzyme B or CD107a. D. Mean percentages plus SEM of PD-1^hi or PD-1^lo tetramer⁺ CD8⁺ T cells expressing the degranulation marker CD107a. Each column represents the mean percentage plus SEM for a group of 5 – 10 mice. Data were pooled from two independent experiments with similar results. Differences were analyzed by the unpaired t-test. Statistically significant differences between the groups are indicated by P values.

E. Representative histograms showing killing of target cells loaded with the FV D^bGagL peptide (CFSE high; +peptide) or control cells without peptide (CFSE low; -peptide) in spleens of naïve or FV infected mice with an H-2^b/b (C57BL/6) or H-2^a/b ((B10.A x A.BY)F1) genetic background. Numbers in the figure indicate the mean percentage of killing for the whole group. Data from one representative mouse of a group of 7 mice are shown. Two independent experiments with similar results were performed.