Intranuclear fibrillary inclusions in influenza pneumonia.

Electron microscopical study of the lung tissue from a 75-year-old man who died of influenza pneumonia (A/Victoria/RI/76) demonstrated fibrillary inclusions in the nuclei of many alveolar lining cells, in bronchial epithelial cells, and also in endothelial cells. These inclusions were morphologically different from those previously reported in experimental animals. In view of previous experimental studies indicating the necessity of nuclear participation in the replication of influenza virus, these inclusions may be virus-induced structures. Also, possibly the presence of these inclusions in the nuclei of many endothelial cells might be indicative of endothelial damage of microvessels and may be a pathogenetically important factor in influenza pneumonia.