Natural killer cells in asthma

Abstract

Purpose of review to discuss current knowledge on natural killer (NK) cells in asthma. Recent findings It is now well accepted that NK cell activities go beyond cancer immune surveillance and anti-viral defense. Recent reports indicate that NK cells are activated in response to allergens in vivo. NK cells promote allergic sensitization, type-2 immune response, development of eosinophilic inflammation and airway hyperresponsiveness. NK cells are activated by RSV and other respiratory viruses. When infection occurs in the setting of active allergic inflammation, NK cells augment its magnitude and contribute to asthma exacerbations. Pro-asthma activities of NK cells can be programmed during embryogenesis through maternal exposure to environmental pollutants. Prenatally-programmed NK cells produce type-2 and type-3 cytokines and mediate asthma predisposition. NK cells can also act as asthma antagonists. NK cells contribute to the resolution of inflammation through suppression of antigen-specific CD4+ T cells and type-3 immunity. When viral infection occurs in naïve mice prior to allergic sensitization, NK cells antagonize type-2 immunity and prevent development of asthma. Summary NK cells are non-redundant participants of allergic inflammation. The environmental context determines whether NK cells act as protagonists or antagonists.

Altered Frequency of NK Cells and Treg Cells by Astragalus Polysaccharide Combined with Budesonide in Asthma Model Mice

“…Some studies have con rmed that NK cell subsets are signi cantly reduced in patients with allergic asthma, suggesting that the occurrence of asthma is related to the inhibition of NK function [15]. Moreover, the NK cells content in the remission phase of asthma was higher than that in the acute attack phase [16,17]. NK cells is a necessary factor for naive T cells di erentiating to 2 cells.…”

The Role of Heat Shock Protein 70 kDa in Asthma

“…56 However, several other studies showed that blocking of NKG2D by antibodies or genetic depletion have not significant influence on the development of asthma in different mouse models. 55 The data shown above suggest, that most of the HSP70binding receptors have other ligands besides HSP70. Data showing that binding of HSP70 to its cognate or other immune receptors affects inflammation in asthma do not yet exist.…”

“…The natural killer (NK) cell receptor, NKG2D, and NK cells are activated in asthma. 55 NKG2D-deficient mice show no signs of allergic airway inflammation after exposure to the HDM allergen. 56 However, several other studies showed that blocking of NKG2D by antibodies or genetic depletion have not significant influence on the development of asthma in different mouse models.…”

Cell-Specific DNA Methylation Signatures in Asthma

“…The impairment of natural killer (NK) cell activity has been seen in individuals with asthma, but the trend of the observed effects (their increased or decreased cytotoxicity) remains controversial [105,106,107]. NK cell activities go beyond their known role in the natural host defence against infectious pathogens.…”

“…NK cell activities go beyond their known role in the natural host defence against infectious pathogens. They also influence the T-cell response, interact with dendritic cells to induce their maturation and produce type 2 cytokines [107,108]. In vitro activation of NK is associated with altered DNA methylation, which reveals similarities with activated T cells, but also shows cell-specific alterations when compared with methylated T and B cells [64].…”