Ultrastructural changes in hamster tracheal ring cultures exposed to Mycoplasma pneumoniae

Ultrastructural studies of lung biopsies in this laboratory from 2 children with chronic respiratory disease and elevated titers to Mycoplasma pneumoniae showed increased pleomorphic lysosomes in alveolar macrophages. This suggested that intracellular digestion might be an important feature of mycoplasma infection and an in vitro study was undertaken. Tracheal ring cultures from 35 Syrian hamsters were exposed to Clyde M129 strain of M pneumoniae. Controls consisted of untreated tracheal rings from the same animals. Both groups were subjected to light, fluorescent, and electron microscopy. Cultures exposed to virulent mycoplasma exhibited specific immunofluorescence at mucosal surfaces and in the submucosa. Mucosal cytopathic changes and submucosal necrosis were prominent. Submucosal macrophages contained increased numbers of lysosomes, some of which contained mycoplasma-like forms. If Mycoplasma pneumoniae are ingested by macrophages, this would provide a mechanism through which immune phenomena could occur and would partially explain the prominent peribronchial lymphocytic accumulation of human mycoplasma infection.