PDCD1 and idiopathic pulmonary fibrosis: Analysis of LGRC gene expression data demonstrated that PD-1 was significantly increased in IPF lungs (n = 123) compared to control lungs (n = 96) (IPF: 9.5, 95% CI: 9.3 to 9.6, vs. controls: 8.9, 95% CI: 8.8 to 9.3, p = 0.001), (Fig. 3, Panel D).