In this study, the serum levels of BAFF, interleukin (IL)-10, and IL-17 were determined in patients with IPAF, CTD-ILD, and IPF, and the correlations among BAFF, IL-17, IL-10, lung function, and alveolar-arterial oxygen pressure difference (AaDO2) were analyzed. The gene discussed is IL17A; the disease is idiopathic pulmonary fibrosis.