Figure 3. Histopathology of lung lesions.

Histopathology was performed on samples derived from human H2N2 and swine H2N3 infected animals on 1, 6 and 14 dpi. The left hand columns (panels A, C, E, G, I, K) are H&E stained sections of lung representative of the three time points. The right hand columns are IHC stained lung sections from the same animal and lung lobe as the H&E stained sections. (A) Inflammatory cells (neutrophils and macrophages) and cell debris in a bronchial lumen (asterisk); similar cell population in adjacent alveoli (white arrow). (B) Antibody positive staining in cells of the bronchial lining epithelium with epithelial cell morphology (arrow). Asterisk indicates bronchial lumen. (C) Alveolar type II pneumocyte hyperplasia (black arrowhead) and fibrin in alveoli adjacent to a bronchus. (D) Rare antibody stained cell in bronchial lining epithelium (arrow). (E) Chronic pneumonia (fibroblasts, lymphocytes, plasma cells) with alveolar septal fibrosis (f) and type II pneumocyte hyperplasia (black arrowhead). (F) Absence of antibody staining. (G) Numerous neutrophils and macrophages within alveoli adjacent to a bronchus (white arrow). Asterisk indicates bronchial lumen. (H) Antibody positive stained cells in bronchial lining epithelium (arrow). (I) Fibrin hyaline membrane (open arrowhead); mixed inflammatory cells and thickened alveolar septae. (J) Rare antibody stained cells with macrophage or possible type II pneumocyte morphology (arrow). (K) Chronic pneumonia (fibroblasts, lymphocytes, plasma cells) and organized fibrin (open arrowhead) within alveoli. (L) Absence of antibody stained cells. Key: A, B = animal 635; C, D = animal 479; E, F = animal 358; G. H = animal 805; I, J = 937; K, L animal 745 (for animal numbers see also Table 1).