FIGURE 7.

IL-1β induces lipocalin 2 and rescues TLR4 KO from KP infection in an IFN-γ-independent manner. A, MLE were stimulated in triplicate with IL-1β with or without TNF-α. Cell lysates were assayed for lipocalin 2 levels by ELISA. B, Three strain controls (WT) and three IL-1R KO mice were infected and lung homogenates were analyzed for lipocalin 2 levels. IL-1R KO mice show decreased levels of lipocalin 2 after infection. C, Six WT and six TLR4 KO mice were infected and another cohort of TLR4 KO mice (six animals) was given IL-1β. Animals were sacrificed at 12 h of infection and lung homogenates were assayed for lipocalin 2. Lipocalin 2 levels in the TLR4 KO again were significantly diminished compared with WT and significantly increased in TLR4 KO mice that received IL-1β. D, TLR4 KO mice receiving IL-1β were rescued from infection as demonstrated by bacterial load after 12 h of infection. E, WT mice up-regulate IFN-γ during infection, but TLR4 KO, including TLR4 KO receiving IL-1β do not; therefore, the mechanism of IL-1β - mediated rescue from infection is not due to IFN-γ up-regulation. *, Statistical significance compared with unstimulated or WT and **, statistical significance compared with untreated KO.