TNF and idiopathic pulmonary fibrosis: Bacteroides stimulate the release of proinflammatory cytokines (e.g., IL-1, CXCL8, IFN-γ, and tumor necrosis factor-α), which can lead to a severe inflammatory response.[36] Bacteroidetes can increase bile acid levels in the liver through 2 pathways: catabolizing bile acids by bile salt hydrolases and causing a decrease in the absorption of bile acids in the ileum.[37] Bile acids can induce the formation of IPF, which is consistent with our results that Bacteroidaceae is positively related to the development of IPF.