PLCL1 and idiopathic pulmonary fibrosis: ‘COL23A1+ adventitial fibroblasts’ shared key markers (COL15A1, ENTPD1, PLCL1) with peribronchial fibroblasts, a subpopulation specifically localized around the airway epithelium, which is enriched in idiopathic pulmonary fibrosis and may be implicated as a key cell type in lung disease (3).