Expression of peroxidase activity in rat tracheal epithelial cells associated with Mycoplasma pulmonis

M. Kinbara, T. Ueda and K. Hirai Department of Anatomy, Kanazawa Medical University, Ishikawa, Japan. Endogenous peroxidase activity has not been localized in the tracheal mucosal epithelial cells of specific pathogen-free (SPF) rats. After natural infection with Mycoplasma pulmonis in SPF rats, peroxidase activity became localized to the endoplasmic reticulum, nuclear envelope, and Golgi apparatus of tracheal ciliated or mucous secretory cells. Some secretory cells occasionally had peroxidase-positive secretory granules. At 1 wk M. pulmonis was found to attach to these epithelial cells, which then showed positive peroxidase activity at 2 wk. Serum antibody titers against M. pulmonis were positive at 5 wk. These results suggest that virulent mycoplasma infection and interaction with the tracheal epithelial cells trigger the de novo expression of peroxidase activity, which seems to play a role in mucosal anti-microbial defense mechanisms.