Lungs are constantly exposed to environmental challenges, making them susceptible to infection and injury. For this reason, they are protected by specialized cells that can respond rapidly to danger signals. Amongst these cells are innate lymphoid cells (ILCs) that include three main subsets: group 1, group 2 and group 3 ILCs. To date, the majority of the studies have focused on ILC2s and their importance in allergy and tissue repair. However, it is now becoming evident that ILC3s play a key role in lung health. In fact, ILC3s have recently been shown to accumulate in the lung after Mycobacterium tuberculosis infection and in an obesity-induced asthma disease. Accordingly, preliminary results show that the accumulation of ILC3s in the lung is mediated by IL-1b, yet the mechanisms inducing ILC3s in the lung and their function remain unclear. This project will provide an extensive analysis of the origin and functions of ILC3s in naive and inflamed lungs, with an ultimate goal of translating our findings to a wide range of lung diseases, which are life-limiting and still a major cause of death in young, elderly, immune-compromised and cystic fibrosis patients.