Tregs may enhance EMT and contribute to the progression of pulmonary fibrosis by secreting cytokines such as PDGF and TGF-β, or curb its progression by facilitating the repair of damaged epithelial cells, suppressing fibroblast accumulation, and inhibiting the production and activity of pro-inflammatory factors and cells (141). Here, TGFB1 is linked to pulmonary fibrosis.