Figure 7.

The ability of Streptococcus pneumoniae (Spn) aminopeptidase N (PepN) to inhibit NP-specific cytotoxic T lymphocyte (CTL) effector function is independent of its enzymatic activity. The enzymatic activity of wild-type PepN and PepN^Met− was tested by incubation with lys-AMC. Raw absorbance values from three independent experiments are shown in (A). The average of values normalized to the level of activity observed using wild-type PepN (plotted as % relative activity) is shown in (B). In (C), NP-specific CTL were stimulated in the presence of PepN or PepN^Met−. Cells were stained with anti-CD8 and anti-IFNγ antibodies following the stimulation period. Averaged data ± SEM from three independent experiments assessing the inhibitory activity of each protein is shown. **p < 0.01 and ***p < 0.001.