Immune response in mice infected in the genital tract with mouse pneumonitis agent (Chlamydia trachomatis biovar).

Female Swiss-Webster mice were inoculated intravaginally with mouse pneumonitis agent (MoPn), a Chlamydia trachomatis biovar. Inoculation with 3.5 X 10(5) egg lethal doses per mouse resulted in shedding of the agent from the genital tract for as long as 21 days. Immunoglobulin M antibodies to MoPn were detected in plasma by day 7 post-inoculation, and immunoglobulin G antibodies were detected by day 14. Antibodies were detected in genital secretions by day 20, and titers in plasma and secretions were still considerable on day 56. Delayed-type hypersensitivity tests, determined by footpad swelling, were not positive in appreciable numbers of animals until after day 25. Delayed-type hypersensitivity reactions were maximal 24 h after testing and were preceded by an Arthus-like reaction, which appeared within 3 h and declined by 12 h. Convalescent animals were rechallenged by intravaginal inoculation and were found to be solidly immune.