XBP1 and cystic fibrosis: Consistent with these observations, P. aeruginosa infection in mice induced lung inflammation and UPR activation as measured by splicing of XBP‐1 measured in vivo using the ERAI ER stress‐reporter transgene.49 Development of ER stress is unsurprising as CF lungs are chronically infected and the mucosa and lung secretions contain a broad array of inflammatory cytokines50, 51 many of which are known to drive oxidative stress and therefore ER stress (reviewed in Hasnain et al. 1, 52).