Expression levels of BiP, EDEM, XBP1 (34–60), p50ATF6, ATF6, ATF4, CHOP, and misfolded pro-SP-C mutant protein aggregates in AECs-II can serve as potential diagnostic markers of ER stress in IPF [155,248,251,252]. The gene discussed is XBP1; the disease is idiopathic pulmonary fibrosis.