TGFB1 and pemphigus foliaceus: In addition, activation of the TGF-β1/Smad signaling pathway reduces the secretion and inhibits the activity of matrix protein metallases, while increasing the synthesis and secretion of matrix metalloproteinase tissue inhibitory factor, which inhibits myofibroblast apoptosis and leads to the production of large amounts of ECM and its failure to degrade properly, allowing it to accumulate in the lung and cause PF [36, 101].