Fig. 3. Cytokine levels in lung homogenates. Levels of interleukin (IL) 6, keratinocyte-derived chemokine (KC), IL-10, IL-1α, IL-1β, and tumor necrosis factor (TNF) α in unventilated (C) and ventilated (V) wild-type (WT) and Toll-like receptor (TLR) 4 knockout (KO) mice. Mechanical ventilation in WT mice (group V^TLR4WT) increased KC (  P < 0.0001), IL-1α (  P = 0.003), and IL-1β (  P < 0.0001) in lung tissue homogenates when compared with unventilated WT mice (group C^TLR4WT). In TLR4 KO mice (group V^TLR4KO), mechanical ventilation did not increase IL-1β in lung homogenates. Mechanical ventilation in TLR4 KO mice (group V^TLR4KO) did increase levels of KC (  P = 0.0003) and IL-1α (  P = 0.003) when compared with unventilated TLR4 KO mice (group C^TLR4KO). Ventilated TLR4 KO mice (group V^TLR4KO) showed significantly lower levels of KC (  P < 0.0001) and IL-1β (  P = 0.0005) in lung homogenates compared with ventilated WT mice (group V^TLR4WT). Between unventilated animals, the levels of KC (  P = 0.0069) and IL-1β (  P = 0.048) in lung homogenates were higher in the TLR4 KO mice (group C^TLR4KO) compared with WT mice (group C^TLR4WT). Data are expressed as median with 25th and 75 percentiles (  box ) and range (  whiskers ). *P < 0.05 compared with age-matched unventilated mice. +  P < 0.05 compared with ventilated WT mice (V^TLR4WT). # Compared with unventilated WT mice (C^TLR4WT). −= lower detection limit.