Lawson et al. demonstrated evidence of UPR activation markers (including heavy-chain- binding protein (BiP), ER degradation enhancing α-mannosidase-like proteins (EDEM), and XBP1) in patients with f-IPF expressing the L188Q SFTPC mutation and samples from non-SFTPC f-IPF and s-IPF cases 177. Here, XBP1 is linked to idiopathic pulmonary fibrosis.