Role of Natural Killer Cells in Airway Inflammation

Natural killer (NK) cells have an immune regulatory function as well as cytotoxicity against tumor or infected cells. In the airway, although NK cells constitute a small proportion of the resident lymphocytes, they play an important role in the pathogenesis of chronic inflammatory airway diseases by modulating immune responses. NK cells can promote allergic airway inflammation by increasing the production of type 2 cytokines and inducing eosinophil migration. The increased activity of NK cells can develop or aggravate the destruction of lung parenchymal cells. On the other hand, decreased apoptotic activity of NK cells in eosinophils can serve as an aggravating factor for allergic airway inflammation. The increase in interferon-γ-producing NK cells and the inhibition of type 2 immune response by NK cells can alleviate allergic airway inflammation. This review aims to define the roles of NK cells in chronic inflammatory diseases of lower and upper airways.