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. 2010 Oct 20;17(12):1998–2006. doi: 10.1128/CVI.00247-10

FIG. 3.

FIG. 3.

Priming by seasonal influenza virus infection protected ferrets from severe lung histopathology after H1N1pdm virus challenge. Illustrated are the histopathologic findings associated with the bronchioles and interbronchiolar alveoli and interstitium in the lungs of ferrets challenged with the H1N1pdm virus following various pretreatments (H&E staining, ×20 magnification). (A and B) Lung tissue from a ferret that belongs to the I/M group, which was primed by seasonal H1N1 virus infection prior to receiving a single dose of pMIV. (A) Neutrophils (arrows) and mucus are present in the lumens of two bronchioles. (B) The alveoli (a) are free of inflammatory cells, and the interstitial septa (arrows) are thin and narrow and have very few cells other than red blood cells. (C and D) Lung tissue from a ferret that belongs to the M/M group, which received two doses of pMIV 3 weeks apart prior to the H1N1pdm virus challenge. (C) Mononuclear inflammatory cells (m) fill the lumens of two bronchioles. Due to bronchiole epithelial necrosis and sloughing, one bronchiole is not lined with epithelium (thick arrows), whereas the other bronchiole is lined with some hypertrophied regenerating epithelial cells (thin arrows). There is also a mononuclear cell infiltrate surrounding the bronchioles. (D) Mononuclear inflammatory cells fill several of the alveoli (a) that make up the lung parenchyma between the bronchioles, and the interstitial septa (arrows) associated with the alveoli are thickened with inflammatory mononuclear cells. (E and F) Lung tissue from a control ferret that was challenged with the H1N1pdm virus following pretreatment with PBS. (E) Mononuclear inflammatory cells (m) fill the lumen of a bronchiole that is lined with hypertrophied regenerating epithelial cells (arrows). Alveolar pneumocyte hyperplasia is associated with the alveoli adjacent to the bronchiole, and the alveoli are filled with mononuclear inflammatory cells. (F) The alveolar and interstitium architecture of the lung parenchyma between bronchioles is effaced with infiltrates of mononuclear inflammatory cells and hyperplastic epithelial pneumocytes.