This can explain the relationship between antigen-induced airway obstruction and TGF-β1 levels observed in our study; paradoxically, airway responsiveness and TGF-β1 levels were not associated, suggesting that there are some mechanisms involved in indirect challenge with antigen that are affected by TGF-β1 that are not involved in the direct stimulation of ASM by histamine. The gene discussed is TGFB1; the disease is Airway obstruction.