ILC3s control airway inflammation by limiting T cell responses to allergens and microbes

Group 3 innate lymphoid cells (ILC3s) critically regulate of host-microbe interactions in the gastrointestinal tract, but their role in the airway remains poorly understood. Here we demonstrate that lymphoid tissue-inducer (LTi)-like ILC3s are enriched in the lung-draining lymph nodes of healthy mice and humans. These ILC3s abundantly express major histocompatibility complex class II (MHCII) and functionally restrict the expansion of allergen-specific CD4+ T cells upon experimental airway challenge. In a mouse model of house dust mite-induced allergic airway inflammation, MHCII+ ILC3s limit Th2 cell responses, eosinophilia, and airway hyper-responsiveness. Further, MHCII+ ILC3s limit a concomitant Th17 cell response and airway neutrophilia. This exacerbated Th17 cell response requires exposure of the lung to microbial stimuli, which can be found associated with house dust mites. These findings demonstrate a critical role for antigen-presenting ILC3s in orchestrating immune tolerance in the airway by restricting pro-inflammatory T cell responses to both allergens and microbes.