Demonstration of the effects of transgenic IL-13 on airway fibrosis and mucus metaplasia. (a) Trichrome stains are used to compare the amount of blue-staining collagen around airways from transgene-negative mice (left) and transgene-positive mice (right). (b) Alcian blue stains are used to demonstrate mucus accumulation in airways from transgene-negative mice (left) and transgene-positive mice (right). Mucus is blue in this evaluation.