Directing traffic: IL‐17 and IL‐22 coordinate pulmonary immune defense

JP McAleer, JK Kolls - Immunological reviews, 2014 - Wiley Online Library
Immunological reviews, 2014Wiley Online Library
Respiratory infections and diseases are among the leading causes of death worldwide, and
effective treatments probably require manipulating the inflammatory response to pathogenic
microbes or allergens. Here, we review mechanisms controlling the production and
functions of interleukin‐17 (IL‐17) and IL‐22, cytokines that direct several aspects of lung
immunity. Innate lymphocytes (γδ T cells, natural killer cells, innate lymphoid cells) are the
major source of IL‐17 and IL‐22 during acute infections, while CD 4+ T‐helper 17 (Th17) …
Summary
Respiratory infections and diseases are among the leading causes of death worldwide, and effective treatments probably require manipulating the inflammatory response to pathogenic microbes or allergens. Here, we review mechanisms controlling the production and functions of interleukin‐17 (IL‐17) and IL‐22, cytokines that direct several aspects of lung immunity. Innate lymphocytes (γδ T cells, natural killer cells, innate lymphoid cells) are the major source of IL‐17 and IL‐22 during acute infections, while CD4+ T‐helper 17 (Th17) cells contribute to vaccine‐induced immunity. The characterization of dendritic cell (DC) subsets has revealed their central roles in T‐cell activation. CD11b+ DCs stimulated with bacteria or fungi secrete IL‐1β and IL‐23, potent inducers of IL‐17 and IL‐22. On the other hand, recognition of viruses by plasmacytoid DCs inhibits IL‐1β and IL‐23 release, increasing susceptibility to bacterial superinfections. IL‐17 and IL‐22 primarily act on the lung epithelium, inducing antimicrobial proteins and neutrophil chemoattractants. Recent studies found that stimulation of macrophages and DCs with IL‐17 also contributes to antibacterial immunity, while IL‐22 promotes epithelial proliferation and repair following injury. Chronic diseases such as asthma and chronic obstructive pulmonary disease have been associated with IL‐17 and IL‐22 responses directed against innocuous antigens. Future studies will evaluate the therapeutic efficacy of targeting the IL‐17/IL‐22 pathway in pulmonary inflammation.
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