IL17A and idiopathic pulmonary fibrosis: In particular, three pathways: Th1 Pathway, Differential Regulation of Cytokine Production in Macrophages and T Helper Cells by IL-17A and IL-17F pathway, and Differential Regulation of Cytokine Production in Intestinal Epithelial Cells by IL-17A and IL-17F were found to be significantly associated with IPF under all models.