Interleukin-17 (IL-17),a member of the IL-17 cytokine family,plays a crucial role in mediating the immune response against extracellular bacteria and fungi in the lung.Although there is increasing evidence that IL-17 is involved in protective immunity against H 1 and H3 influenza virus infections,little is known about the role of IL-17 in the highly pathogenic H5N 1 influenza virus infection.In this study,we show that H5N1-infected IL-17 knockout (KO) mice exhibit markedly increased weight loss,more pronounced lung immunopathology and significantly reduced survival rates as compared with infected wild-type controls.Moreover,the frequency of B cells in the lung were substantially decreased in IL-17 KO mice after virus infection,which correlated with reduced CXCR5 expression in B cells and decreased CXCL13 production in the lung tissue of IL-17 KO mice.Consistent with this observation,B cells from IL-17 KO mice exhibited a significant reduction in chemokine-mediated migration in culture.Taken together,these findings demonstrate a critical role for IL-17 in mediating the recruitment of B cells to the site of pulmonary influenza virus infection in mice.
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