In addition to its effects on immunity, TGF-β activation during influenza infection promotes epithelial cell apoptosis and collagen deposition, dependent on Smad3 and αvβ6 integrin, suggesting that TGF-β could contribute to the potential pro-fibrotic sequelae of influenza infection.50 TGF-β from diverse cellular sources therefore acts via context-specific mechanisms to govern the outcomes of influenza infection. Here, SMAD3 is linked to influenza.