Innate lymphoid cells in asthma: pathophysiological insights from murine models to human asthma phenotypes

The current review describes the role of different types of innate lymphoid cells (ILCs) in the pathogenesis of asthma inflammatory phenotypes by linking findings from murine asthma models with human studies. Novel treatment options are needed for patients with steroid-insensitive asthma. Strategies targeting ILCs, or their upstream or downstream molecules are emerging and discussed in this review.

In eosinophilic asthma, ILCs, and especially type 2 ILCs (ILC2s), are activated by alarmins such as IL-33 upon allergen triggering of the airway epithelium. This initiates IL-5 and IL-13 production by ILC2, resulting in eosinophilic inflammation and airway hyperreactivity. Type 3 ILCs (ILC3s) have been shown to be implicated in obesity-induced asthma, via IL-1β production by macrophages, leading ILC3 and release of IL-17. ILC1s might play a role in severe asthma, but its role is currently less investigated.

Several studies have revealed that ILC2s play a role in the induction of eosinophilic inflammation in allergic and nonallergic asthmatic patients mainly via IL-5, IL-13, IL-33 and thymic stromal lymphopoietin. Knowledge on the role of ILC3s and ILC1s in asthmatic patients is lagging behind. Further studies are needed to support the hypothesis that these other types of ILCs contribute to asthma pathogenesis, presumably in nonallergic asthma phenotypes.