Mitogenicity and pathogenicity of Mycoplasma pulmonis in rats. I. Atypical interstitial pneumonia induced by mitogenic myeoplasmal membranes.

Mitogenic preparations of nonviable lysed cells and purified membranes of Mycoplasma pulmonis induced interstitial pneumonia and tracheitis after intranasal administration to pathogen-free rats. The pneumonia, characterized by peribronchial, perivascular, and alveolar wall infiltration by lymphocytes, was indistinguishable from that produced by viable M. pulmonis. Both pathologic and mitogenic effects were significanlty reduced by prior treatment of membranes with heat or proteolytic enzyme. Intranasal administration of the thymus-derived-cell mitogen, concanavalin A, produced interstitial pneumonia but not tracheitis. These results indicate a correlation of mitogenicity and pathogenicity and suggest that activation of thymus-derived lymphocytes is the major cause of the pneumonia resulting from infections with M. pulmonis.