DDIT3 and idiopathic pulmonary fibrosis: The UPR markers GRP78, ERAD-enhancing α-mannosidase-like proteins, XBP1, CHOP, ATF4 and ATF6 have been detected at elevated levels in the lungs of IPF patients, especially in alveolar type II epithelial cells (Korfei et al., 2008; Lawson et al., 2008).