The early cytokine response to S. aureus is reduced in the airways of tlr9−/− mice. (A–C) Cytokine (TNF-α, IL-6 and IL-1β) levels in BALF at different time points after intranasal infection of 1 × 107 CFU S. aureus in Wt mice (gray) and tlr9−/− mice (white). Data are expressed as box-and-whisker diagrams depicting the median, the smallest observation, lower quartile, median, upper quartile and largest observation (n = 7–8 mice per group at each time point). *p < 0.05, **p < 0.01 versus Wt mice at the same time point.