FIG. 4.

Mean (SEM) TNF-α, IL-1α, and IL-6 levels in cell-free BAL fluid 12 and 24 h after intranasal inoculation of mice with 3.5 × 10⁷ CFU of S. pneumoniae. Animals that were sacrificed at 12 h received a single injection of L-NMMA (3 mg/kg s.c.) at time zero, while animals that were sacrificed at 24 h received a second injection at 12 h. Comparisons indicated by the asterisks (∗, P < 0.05; ∗∗, P < 0.01; and ∗∗∗, P < 0.001) were made between infected animals and their respective uninfected controls (infected versus control and infected plus L-NMMA versus L-NMMA). Negligible amounts of cytokines could be detected in uninfected mice.