FIG. 1.

Pneumolysin is essential for the secretion of IL-1α, IL-1β, and IL-18 in response to Streptococcus pneumoniae. Peritoneal macrophages were left uninfected (UI) or infected with wt S. pneumoniae (Sp wt) or the ply mutant (Δply) at a macrophage/bacterium ratio of 1:10 for 8 h. Cells were cultured for an additional 16 h in the presence of gentamicin (100 μg/ml), and culture supernatants were then collected. The amounts of IL-1α (A), IL-1β (B), IL-18 (C), TNF-α (D), IL-6 (E), and IL-12p40 (F) were determined using ELISAs specific for each cytokine. The results are representative of three similar experiments. The data are the means ± standard deviations for three determinations. *, P < 0.05 for uninfected cells compared to wt S. pneumoniae-infected cells and for wt S. pneumoniae-infected cells compared to Δply mutant-infected cells.