Influences of intrauterine semen administration on regulatory T lymphocytes in the oestrous mare (Equus caballus).

This research study investigated the effect of seminal plasma and raw semen on the immune system’s response in horses that are in heat. Specifically, the response of regulatory T cells in both the endometrium and peripheral blood was observed. Only small changes were found in the response of these cells, leading the researchers to conclude that these factors are not strongly involved in the mare’s ability to sustain a pregnancy.

Objective of the Research

• The study aimed to explore the role of the maternal immune system and its potential involvement in early pregnancy loss in horses. Specifically, the researchers focused on the response of regulatory T cells when the mare’s endometrium is exposed to semen or seminal plasma.

Method

• A total of 12 horses in heat were included in the study. Each mare received either raw semen, seminal plasma, or PBS (used as a control) into their uterus.
• Blood samples were taken before the introduction of any substance (time 0), and then 12, 24, and 48 hours afterwards. At 24 hours, endometrial biopsies were also collected.
• Regulatory T cells in the peripheral blood was determined using flow cytometry, while cells in endometrial biopsies were assessed through immunohistochemistry. Cells staining positive for Foxp3 were tagged as T cells.

Findings

• The researchers found that the portion of regulatory T cells in blood decreased 12 hours after exposure to seminal plasma. The reduction was slight, almost reaching significance in the case of raw semen, but wasn’t seen when PBS was used.
• No changes were observed in leukocyte and PMN counts. Similarly, the number of Foxp3 positive cells in the endometrium didn’t show any deviation 24 hours after insemination or PBS infusion, regardless of the treatment provided.

Conclusion

• The minimal changes observed suggest that the mare’s tolerance to pregnancy in the early stages is not significantly influenced by exposure of the endometrium to seminal plasma during mating. This contradicts previous suspicions that seminal plasma may have a stronger role in either promoting or inhibiting the ability of the mare to sustain early pregnancy.