DYNAMIC CHANGES IN THE LYMPHOCYTE SUBPOPULATIONS OF PIG UTERINE LYMPH-NODES

Cell subpopulations in local lymph nodes draining the uterine tissue o f non-pregnant and pregnant pigs were examined by one- and two-colour immunofluorescent staining and flow cytometry using a panel of monoclo nal antibodies to pig leucocyte cell surface antigens. Significant cha nges were observed in the T and B lymphocyte subpopulations and in a s ubpopulation of non-T or B cells. Activation of lymphocytes in the ute rine lymph nodes during cycling in non-pregnant gilts suggests a role for the local immune system in the normal physiology of the uterus. In non-pregnant sows there was evidence of an increase in the CD4/CD8(H) ratio and in the proportion of B cells in the uterine nodes when comp ared to gilts with no prior reproductive experience. Pregnancy was sho wn to induce further dramatic changes in the uterine lymph nodes with an escalation in the proportion of B cells from 48% to 88% and a furth er increase in the CD4/CD8(H) ratio. For the first time in swine, low- level CD2 expression is reported on a subpopulation of B cells which a re activated during pregnancy. These results provide evidence that the local uterine immune system in pigs plays a role in reproduction and perhaps in the maintenance of normal pregnancy.