ing in vitro and in vivo The IL-17 pathway has recently been implicated in host defense against a number of both intra- and extra-cellular pathogens. IL17A is known to be required for host defense and inflammation in response to gram-negative and gram-positive bacteria, as well as Influenza A infection. In models of bacterial pneumonia IL-17R signaling or IL-17A is required for pathogen clearance. In contrast in Influenza A infection, IL-17R signaling is dispensable for viral clearance, but is required for morbidity and lung injury. Since JNK1 has a role in these infection paradigms and JNK1 2/ 2 mice had a trend towards decreased IL-17A production, the role of JNK1 in IL-17A signaling was investigated. First, to confirm that IL-17A stimulates JNK1 activity, mouse tracheal JNK1 and Host Defense epithelial cells were treated with IL-17A and JNK1 phosphorylation of c-Jun was determined. IL-17A induced rapid activation of JNK1 as early as fifteen minutes after stimulation. IL-17A is known to stimulate inflammatory cytokine and antimicrobial peptide production by epithelial cells. WT and JNK1 2/2 MTEC were stimulated with IL-17A for one 9140707 day and cytokines were measured by multiplex cytokine assay and RTPCR. IL-17A induced KC and MIP-2 protein and mRNA as well as decreased IP-10 protein were significantly decreased in JNK1 2/2 MTEC compared to WT cells. Surprisingly, JNK1 2/2 MTEC had increased G-CSF mRNA, but no change in protein compared to WT cells, upon stimulation with IL-17A. These data demonstrate that JNK1 is required for IL17A pro-inflammatory signaling in vitro. In addition, JNK1 2/2 MTEC expressed significantly decreased levels of the antimicrobial peptides S100a8 and Defb4 compared to IL-17A stimulated WT MTEC. Taken together, the data suggest that IL17A signals through JNK1 to induce inflammation and enhance host defense. Since JNK1 was shown to play a role in IL-17A signaling in vitro in epithelial cells, the impact of JNK1 deletion on IL-17A signaling in vivo was investigated. WT and JNK1 2/2 mice were challenged with adenovirus expressing IL-17A for three days. Adenoviral IL-17A induced similar levels 11861323 of IL-17A protein in the lung; 4088.161069.5 pg/ml in WT mice and 4009.46459.0 pg/ ml in JNK1 2/2 mice. The total numbers of inflammatory cells in the BAL were similar in WT and JNK1 2/2 mice, however, JNK1 2/2 mice had significantly increased macrophage and decreased neutrophil recruitment. In addition to altered cellular infiltrate profiles, JNK1 2/2 mice produced significantly decreased MCP-1 and IFNc compared to WT mice. The adenoviral expression approach utilized introduces the potential Chebulinic acid caveat of a differential viral response in the WT and JNK1 2/2 mice. To further examine IL-17A 
signaling in vivo, WT and JNK1 2/2 mice were instilled with recombinant mouse IL-17A for one day. IL-17A induced significantly decreased MCP-1 and G-CSF production, as well as a trend towards lower IP-10 and IFNc, in JNK1 2/2 mice versus WT mice. Furthermore, JNK1 2/2 mice stimulated with IL-17A demonstrated a trend towards decreased antimicrobial peptides S100a8 and S100a9 compared to WT mice. These data show that IL-17A requires JNK1 for inflammatory signaling in vivo. Discussion The results of this study indicate that JNK1 plays a context dependent role in host defense and inflammation. In general, JNK1 was associated with macrophage recruitment in response to each of the three pathogens tested. Furthermore, JNK1 was necessary for induction of M