In ruminants, the best described such example is the role of interferon-gamma in the reproductive tract. The normal endometrium is capable of mounting a local response to invading pathogens, thereby maintaining a sterile environment. To initiate immune response, it is necessary to have cells present for antigen recognition and presentation to immunoregulatory lymphocytes and macrophages. Endometrial lymphocytes are intraepithelial lymphocytes with functional characteristics similar to those in the gut. Females treated with progesterones are more likely to develop infections after intrauterine installation of bacteria.
Progesterone inhibits endometrial lymphocyte proliferation and myometrial contractility.
The majority of inflammatory lesions of the uterus commences in the endometrium as endometritis and is associated with either parturition or mating. Infectious agents may enter the uterus as ascending infection from the caudal parts of the reproductive tract, or hematogenously. Ascending infection occurs especially in the mare. There is usually severe destruction of the endometrium allowing for sepsis to occur. Figure 35 Venereal Camylobacteriosis Postcoital infection with Campylobacter fetus venerealis is relatively rare and leads to a rather inconspicuous endometritis macroscopically.