CELLULAR IMMUNE-RESPONSES IN THE PIG UTERUS DURING PREGNANCY

In pigs, little is known about the role of the uterine immune system d uring pregnancy. Immunohistochemical studies were conducted using a pa nel of monoclonal antibodies to pig leukocytes on uterine tissues take n from gilts after fertile mating and at different stages of pregnancy . Acute inflammation in the endometrium in response to fertile mating which included marked changes in the tissue and immune cell components of the endometrium was observed. Throughout pregnancy the pig uterus contained a substantial population of leukocytes. MHC class II stainin g was prominent in the endometrium at all stages examined and included macrophages, dendritic and fibroblast-like cells, lymphocytes and the endothelial lining of many uterine blood vessels. The majority of lym phoid cells were CD2(+), indicating the prevalence of T cells. In earl y pregnancy specific changes were seen in the tissue distribution of u terine immune cells. Following placentation distinct cellular changes in the local immune cell environment of the uterus were also observed despite the non-invasive nature of the pig placenta. There appears to be suppression and activation of various immune cell components in the uteri of pregnant pigs. This phenomenon is presumably in response to foetal or trophoblast antigens, suggesting that the local immune syste m is involved in the uterine response to pregnancy.