[Experimental study on the mechanisms of Chlamydia pneumoniae respiratory infection in mice with former chlamydial exposure].

To compare the differences in the severities, host defense responses and clinical courses C. pneumoniae respiratory tract infections between the initial and second challenge of chlamydia, an experimental C. pneumoniae respiratory infection model using mice was established and the following studies were carried out. For the initial infection mice were challenged with C. pneumoniae, strain TW-183, by nasal instillation. No animals died from this initial infection. The second exposure to C. pneumoniae, in the same manner, was done 35 days after the first challenge. Serial observation in the two groups of mice were done on the anti-C. pneumoniae IgG and IgM antibody titers of their sera, histopathological evaluations of their lungs and the formation of inclusion bodies in the lung sections. Focal inflammatory changes consisting of neutrophil and macrophage infiltration in the alveolar spaces of mice lungs three days after the initial challenge were observed, but there were no remarkable inflammatory changes in the lung sections of mice with the second challenge, with the exception of marked formation of bronchus-associated lymphoid tissues and perivascular accumulation of lymphoid cells. The numbers of inclusion bodies were very small in the lungs of mice with reinfection with chlamydia. These histopathological findings all disappeared within ten and five days after the initial and the second challenge, respectively. Anti-C. pneumoniae IgG antibodies showed a remarkable increase from seven days after the initial challenge and peak value was 1:512-1024 at 28-35 days.(ABSTRACT TRUNCATED AT 250 WORDS)