TGF-β has multiple effects in the lung, including anti-inflammatory activity attributable to its induction of T regulatory cells and pro-fibrotic activity attributable to its effects on fibroblasts 17–23, so that its influence on asthma outcomes, such as AHR, airway eosinophilia and airway remodelling (peribronchial fibrosis and epithelial mucins), can vary depending on the specifics of the mouse model and the mechanism of TGF-β manipulation. The gene discussed is TGFB1; the disease is asthma.