Immunity to mycoplasmal infection of the genital tract: a mouse model.

Thirty-three TO mice, 24 of which had received progesterone, were infected originally by Mycoplasma pulmonis given vaginally. Thirty-one of the mice were free of the organisms in the genital tract 236 days later at which time all of them were treated again with progesterone and rechallenged with M. pulmonis vaginally. All 31 mice were resistant. In contrast, of 21 TO mice of the same age that were not infected originally 15 (71%) became infected persistently after vaginal rechallenge. In similar experiments, 12 CBA mice, nine of which had received progesterone, were infected originally. Ten of these mice were free of the organisms genitally 2 years later, at which time all of them were rechallenged vaginally. Only two mice (20%) were reinfected, whereas six (86%) out of seven mice, not infected originally, were reinfected. Autopsy examination revealed that neither infection nor immunity was confined to the lower genital tract. Thus, M. pulmonis organisms were not detected in the upper tract of five TO mice that remained mycoplasma-free vaginally after rechallenge. The contribution of oropharyngeal M. pulmonis infection, which occurred in most of the mice, to the solid, long-lasting genital-tract resistance was difficult to assess, but in two mice, at least, immunity was not afforded by such infection.