(40× magnification). NAC can alleviate inflammatory infiltration in lung tissue compared with model mice. NAC-L, low-dose 1.73 mg/20 g of N-acetylcysteine; NAC-M, moderate-dose 3.46 mg/20 g of N-acetylcysteine; NAC-H, high-dose 5.19 mg/20 g of N-acetylcysteine. Asterisk indicated bronchial; black pentagon indicated spindle cells; red arrow indicated neutrophils; black arrow indicated macrophages (multinucleated, mononuclear, granular); red ring indicated tissue hyperplasia; red triangle indicated plasma cells; and black triangle indicated lymphocytes.