Gene expression of tumor necrosis factor-.ALPHA. and interferon-.GAMMA. in the lungs of Mycoplasma pulmonis-infected mice.

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Abstract
ICR mice were infected intranasally with Mycoplasma pulmonis isolated freshly from the lungs of the rats with pneumonia. We demonstrated with high reproducibility the expressions of messenger RNAs of cytokines, tumor necrosis factor alpha (TNF-alpha) and interferon-gamma (IFN-gamma) in the lung tissue of M. pulmonis-infected mice. Both the viable population of M. pulmonis in the lung tissue and the titers of the neutralizing antibody in the serum increased in 7 and 14 days, respectively, and reached their maxima in 35 days after infection. Macroscopical and microscopical lesions were evident in the lungs of the mice inoculated with M. pulmonis and sacrificed in 21 days after the inoculation. Microscopically, mild infiltration of mononuclear cells and neutrophils in peribronchial and perivascular spaces were observed. The alveolar septa were swollen with infiltration of these cells. Next, mRNAs prepared from the lung tissues of M. pulmonis-infected and -uninfected mice were tested for the presence of messages specific to TNF-alpha and IFN-gamma by the reverse transcriptase-polymerase chain reaction. The expression of the genes encoding TNF-alpha and IFN-gamma was constitutively demonstrated from 24h through 35 days after the intranasal inoculation of M. pulmonis. Furthermore, cells of two types, adherent and nonadherent cells, in bronchoalveolar lavage fluids obtained from the mice 3 weeks after inoculation of M. pulmonis were found also to express the genes of TNF-alpha and IFN-gamma. These data suggest that these cytokines would play a role in both stimulation and inhibition in the development of pathological changes in mycoplasmal infection, affecting the inflammatory responses.

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