CFTR and cystic fibrosis: Extract of Alternaria, a ubiquitous fungal aeroallergen, was used as the airway antigen challenge, as it is a common fungal sensitizing antigen in CF (24), is associated with strong bronchial provocations in CF (25), and elicits a strong type 2 airway immune response, greater in Cftr deficient compared with Cftr sufficient mice (15).