There is increasing evidence to demonstrate TGF-β1 as the key immunoregulatory cytokine of epithelial cells, which interacts with various immune cells in airway inflammation.22, 23, 24 Upon exposure to antigen, TGF-β1 may be derived from regulatory T (Treg) cells or HAECs with/without interacting with neutrophils.22, 25 TGF-β1 can modulate lineage differentiation of T cells depending on the milieu.23 This evidence concerns the gene TGFB1 and inflammatory response.