Fig. 5

Influence of IL-2 treatment on NK cell effector function and FV control. Mice were infected with FV and several mice were either Treg-depleted by repeated injections of DT and/or stimulated with IL-2/anti-IL-2 mAb complex to specifically stimulate NK cells. At 12 dpi frequencies of splenic NK cells were determined by flow cytometry (a). The proliferation of NK cells was measured by the intracellular expression of Ki-67 (b) and the activation of NK cells was analyzed by surface expression of CD69 (c). The maturation profile was determined by surface expression of KLRG1 (d), CD11b and CD27 (e). Statistically significant differences between the three groups in a–d were determined either by Kruskal–Wallis one-way analysis and Dunn’s multiple comparison tests or by the ordinary one-way ANOVA. Statistically significant differences in e analyzed by Mann–Whitney test could be detected between FV and both treated groups (CD27⁻CD11b⁺ **p < 0.01, CD27⁺CD11b⁻ **p < 0.01), but no significant differences were detectable between IL-2/anti-IL-2 mAb complex-treated groups. At least seven mice per group from at least two independent experiments were used and indicated by mean (±SEM) values and individual dots. f Viral loads during FV infection and treatment with either IL-2/anti-IL-2 mAb complex or isotype control were analyzed by infectious center assay. NK cells were depleted by injections of supernatant fluid containing NK1.1-specific monoclonal antibody PK136. Viral loads were analyzed in NK cell-depleted and IL-2/anti-IL-2 mAb complex treated mice. FV-infected mice were also depleted of CD4⁺ and CD8⁺ T cells or Tregs and several mice were additionally stimulated with IL-2/anti-IL-2 mAb complex. Results are indicated by mean (±SEM) values and dots. At least six mice per group were analyzed in two independent experiments. Statistically significant differences within the T cell-competent groups (FV/FV+Isotype, FV+IL-2/anti-IL-2) and the T cell-depleted groups (FV+DT, FV+DT+IL-2/anti-IL-2, FV+anti-CD4+anti-CD8, FV+anti-CD4+anti-CD8+IL-2/anti-IL-2) were tested using Mann–Whitney test and indicated by single asterisk for p < 0.05, double asterisk for p < 0.01 and triple asterisk for p < 0.001 and ns not significant.