Histology and ultrastructure of metaplasia of alveolar epithelium following infection of mice and hamsters with influenza virus.

Mice and hamsters were infected with the NWS strain of influenza virus and metaplastic changes which developed in the lungs during the healing phase were studied by histology and electron microscopy. Transformation of alveolar epithelium occurred in many animals, producing alveolar epithelialization. This was due to replacement of the normal alveolar epithelium by ciliated columnar and cuboidal cells of bronchiolar type. Squamous changes also developed in healing lungs during the 11-22 day period after infection. Since these lesions regressed later and the cells did not metastasize they were considered to be metaplastic rather than neoplastic in nature.