Chlamydia trachomatis pneumonitis in the C57BL/KsJ mouse: pathologic and immunologic features.

Pneumonitis occurred in both normal and diabetic C57BL/KsJ mice, inoculated with a Chlamydia trachomatis strain isolated from a human infant . Animals were inoculated intranasally under light ether anesthesia. Control animals receiving carrier medium did not develop pulmonary disease. The pneumonitis was focal and involved interstitial and peribronchial structures. Pathological changes were most pronounced at 10 to 14 days after inoculation, but no animals died of their disease. The early cellular response was polymorphonuclear (4 to 6 days); this was followed by a predominantly mononuclear cell infiltrate. Immunopathological examination revealed immunoglobulin- and complement-bearing cells in a peribronchial distribution, corresponding to the mononuclear infiltrates seen by light microscopy. Infected animals seroconverted to C. trachomatis. Specific antichlamydial IgM antibody was detected at days 6 through 21 and higher titer IgG at days 10 through 28. Splenic lymphocyte stimulation responses to chlamydial antigen were observed at 10 and 21 days. C. trachomatis was cultured only from 6-day lung tissue. The histopathological and immunopathological features of the pneumonitis were similar in normal and diabetic mice. In addition, humoral and cellular immunoresponsiveness to chlamydial infection were not compromised in the diabetics. This animal model resembles human infant chlamydial pneumonitis in its pathological manifestations and may increase our understanding of the human disease.