The McKenzie and Locksley laboratories described a similar population that expanded in response to IL-25 and IL-33, produced large amounts of IL-13, and was important for immunity to helminths.17,19 Subsequently, the Umetsu and Stockinger laboratories reported an important role for ILC populations in driving airway inflammation in mice.23,42 In contrast, Monticelli et al21 have reported that a lung ILC population is important for airway remodeling and maintenance of epithelial integrity and lung function after viral infection. Here, IL33 is linked to viral infectious disease.