Masson s trichrome blue

Bronchoalveolar lavage (BAL) was performed 24 hours after the last RV1B challenge. Part of the lung was kept in RNAlater solution (Invitrogen, San Diego, CA) for RNA isolation, and the other part was snap-frozen and homogenized for analysis of total lung collagen using Sircol^™ Assay kit (Biocolor Assay, UK). For lung histology, 5 to 6-μm sections were cut and stained with hematoxylin and eosin (H&E) for examining cell infiltration. Magnification ×200 was used for histologic scoring, and at least 5 fields were scored to obtain the average for each mouse. For airway remodeling analysis, paraformaldehyde-fixed lung sections were stained with Masson's Trichrome blue or anti–alpha-smooth muscle actin (Sigma) and scored with an image analysis system (Image-Pro Plus, Media Cybernetics, Rockville, Md).^{22 (link),23 (link)} In some experiments, smooth muscle thickness was also evaluated using immunofluorescence staining as described elsewhere.^{23 (link)} Results using gene-deficient mice or blocking reagents are expressed as induced responses above background levels in naïve unmanipu-lated mice.