Leucocyte population changes in the reproductive tract of the ewe in response to insemination

Leucocyte changes after insemination may affect conceptus implantation, but information regarding leucocyte populations in the ruminant reproductive tract is limited. The present study investigated changes in leucocyte populations and distribution in the ovine reproductive tract following oestrus and insemination. Fifteen ewes were mated with a ram for 1 h and their reproductive tracts collected 3, 6, 18, 24 or 48 h later. Another 15 ewes were used as oestrus controls. Tissues were collected from 10 sites in each reproductive tract and stained with haematoxylin and eosin, Toluidine blue and immunohistochemically using a monoclonal CD68 antibody. Luminal mucus smears were collected from seven sites and stained with a modified Wright's stain and immunohistochemically. Neutrophils, eosinophils, mast cells and macrophages were identified and quantified, and temporal changes in their distribution within tissues were examined. Neutrophils and macrophages increased significantly (P < 0.05) in posterior cervical and uterine tissues following insemination. In uterine tissues, neutrophils peaked at 6 h after insemination, whereas macrophages peaked at 18-24 h. Mast cells decreased and eosinophils remained constant. Neutrophils increased significantly (P < 0.05) in the cervical and uterine lumen following insemination. In conclusion, leucocyte population changes after insemination vary between different sites in the ovine reproductive tract and may contribute to pregnancy establishment.