IL-17 and Mucosal Immunity

IL-17 is produced by a subset of T-cells (Th17 cells) which are regulated by TGF-b, IL-6 and IL-23. Effector molecules produced by these cells include IL-17A, IL-17F, IL-22 and IL-26. IL-17R signaling is dispensable for host defense against the intracellular pathogens M. tuberculosis and L. monocytogenes but is critical for extracellular pathogens such as K. pneumoniae. In this latter model IL-17 regulates both the granulopoietic response to the infection as well as local CXC chemokine and antimicrobial peptide production in mucosal tissue. These data suggest that the Th17 cell lineage is critical for mucosal host defense against extracellular pathogens.