CD4 and idiopathic pulmonary fibrosis: The PD-1/PD-L1 pathway is currently one of the main targets of immunologic drugs for the treatment of lung cancer, and some studies have shown that IPF patients with concurrent enlarged lymph nodes have higher PD-1 expression and CD4/CD8 ratios, whereas pembrolizumab shows antifibrotic effects in the bleomycin model in mice [33, 34].