An immunohistological study of MHC class II expression and T lymphocytes in the endometrium of the mare.

This study investigates the distribution of T lymphocytes and cells carrying MHC Class II antigens in the endometrium of the mare, finding that several types of cells possess these markers and that they significantly increase during oestrus.

Research Methods

• The study used an avidin-biotin-peroxidase staining method to analyze the distribution of T lymphocytes and of cells bearing MHC Class II antigens in the endometrium of the mare.
• The different cells within the endometrium that were found to express MHC Class II were macrophages, lymphocytes, monocytes, dendritic cells, epithelial cells, and endothelial cells.

Key Findings

• MHC Class II expression significantly increased in the luminal epithelium during oestrus and showed a trend of increasing in the subepithelial layers.
• The numbers of T lymphocytes did not differ between oestrus and dioestrus, the two phases of the mare’s estrous cycle.
• There was no significant difference in MHC Class II expression and T lymphocyte numbers in samples collected on Day 14 of dioestrus and on Day 14 of pregnancy.
• However, the presence of endometritis, an inflammation of the inner lining of the uterus, greatly increased MHC Class II expression and T lymphocyte numbers within the endometrium.

Implications

• The findings suggest that oestrus, the phase of the estrous cycle when the mare is sexually receptive, leads to an increase in the expression of MHC Class II in certain cells of the endometrium.
• The presence of endometritis leads to a significant increase in both MHC Class II expression and T lymphocyte numbers. This is likely a response to inflammation and may affect the mare’s fertility.