Figure 2.

Apoptosis in lung tissues of mice infected with S. pneumoniae D39 serotype 2. (A) Distribution patterns of PLY and apoptosis in representative lung sections from mice intranasally infected with S. pneumoniae D39 serotype 2. PLY was established by staining with anti-PLY rabbit antibodies. Apoptosis was assessed by active caspase-9 staining and in situ TUNEL assay. No staining was observed in lung tissues from uninfected mice. At 12 h post-infection, resident alveolar macrophages were positively stained with anti-PLY, anti-caspase-9, and TUNEL (arrow heads). Infiltrating leukocytes (24 h post-infection) and bronchial epithelium (48 h post-infection) were stained with anti-PLY, anti-caspase-9, and TUNEL, respectively (arrow heads). Note non-stained vascular endothelium. Blood vessel (v), alveolar space (a), bronchiole (b). Scale bars 50 μm. (B) Apoptosis and PLY in lung tissues from untreated mice during pneumococcal pneumonia. Apoptosis was identified by immunohistochemical detection of active caspase-9 and by in situ TUNEL assay. PLY was stained with anti-PLY rabbit antibodies. Adjacent sections were co-stained for co-localization of PLY, TUNEL, and caspase-9. Five sections were analyzed in each time point. Statistical differences were not found for a comparison of number of PLY, caspase-9, and TUNEL positive cells as determined by two-way ANOVA followed by the Bonferroni test. (C) Comparison of caspase-9 positive cells in lung tissues from anti-PLY IgG-, control IgG-, and PBS-treated mice. Percentage of caspase-9 stained cells was calculated with respect to total cells counted in random areas of lung tissue sections. Results are means ± SD of 3 mice and are representative of three independent experiments. *, P < 0.05 for a comparison of anti-PLY IgG-treated mice with PBS-treated mice, and +,P < 0.05 for a comparison of anti-PLY IgG with control IgG-treated mice, as determined by two-way ANOVA followed by the Bonferroni test.