FIG. 4.

Costimulation of rPLY with the Δply mutant significantly increased IL-1α, IL-1β, and IL-18 production by the Δply mutant. Peritoneal macrophages were left uninfected (UI) or infected with wt S. pneumoniae (Sp wt), the Δply mutant, or rPLY (1 μg/ml) plus the Δply mutant at a macrophage/bacterium ratio of 1:10. The amounts of IL-1α (A), IL-1β (B), and IL-18 (C) in culture supernatants were determined by 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 the Δply mutant versus rPLY plus the Δply mutant.