To stimulate the synthesis of ECM proteins such as collagen, active TGF-β1/2, which is increased following allergen exposure and airway epithelial damage in asthma, binds to the TGF-β receptor (TGFBR)-II which phosphorylates TGFBR-1 that also phosphorylates the intracellular signal transducers Smad2 and 3 [72]. This evidence concerns the gene TGFB1 and asthma.