PPP1R15A and idiopathic pulmonary fibrosis: Assessment of protein level expression of PPP1R15A and BiP by immunohistochemistry of IPF lung sections identified immunoreactive staining for both PPPIR15A (Fig. 2a-c) and BiP (Fig. 2e,f) within areas of fibrosis localised to reactive type II pneumocytes and columnar epithelium.