Likewise, multiple studies have implicated a specific immune checkpoint signalling axis—programmed cell death protein 1 (PD‐1) and the corresponding programmed death‐ligand 1 (PD‐L1)—in the pathogenesis of pulmonary fibrosis (Celada et al., 2018; Geng et al., 2019). Here, PDCD1 is linked to pulmonary fibrosis.