FIG 3.

Microscopic lung sections from pigs infected with various H3N2 viruses at 5 days postinfection. (A) The bronchioles are lined by normal cuboidal epithelium (arrow) and the alveoli are clear (asterisk) in the control group. (B) The bronchiolar and alveolar lumen is filled with large numbers of degenerate and intact neutrophils (asterisks), and moderate interstitial, peribronchiolar, and perivascular lymphocytic infiltration is also seen in the KS-83533N group. (C) Moderate bronchiolar epithelial loss and early regeneration are seen (arrow), and the alveolar and bronchiolar lumen contains small numbers of neutrophils (asterisk) in the KS-91088 group. (D) Moderate to severe bronchiolar epithelial degeneration and necrosis with early regeneration are observed (arrow) in the KS-107824 group. (E) Bronchiolar epithelial necrosis with sloughing of necrotic cells in the lumen was noticed (arrow), and the peribronchiolar and interstitial areas contained moderate numbers of lymphocytes and fewer neutrophils (asterisk) in the KS-110529 group. Scale bars, 50 μm.