Lung Inflammation Histological Analysis

Lungs removed from the chest cavity were fixed by injection of 4% buffered paraformaldehyde into the tracheal cannula at a pressure of 20 cm H₂O and immersed in paraformaldehyde for 24 h. Lobes were sectioned sagitally, embedded in paraffin, cut into 5 μm sections, and stained with H&E for histological analysis. Additional sections were stained with alcian blue/PAS to identify mucus-containing cells. The severity of peribronchial inflammation was graded semiquantitatively for the following features: 0, normal; 1, few cells; 2, a ring of inflammatory cells 1 cell layer deep; 3, a ring of inflammatory cells 2–4 cells deep; 4, a ring of inflammatory cells of >4 cells deep. The numerical scores for the abundance of PAS-positive mucus-containing cell in each airway were determined as follows: 0, <0.5% PAS-positive cells; 1, 5–25%; 2, 25–50%; 3, 50–75%; 4, >75% (28 (link)).