Suppression of lymphocyte reactivity by culture supernatant from horse embryos and endometrium.

This research investigates the mechanisms that allow a mare’s body to tolerate the foreign body of a developing foetus. The study observed that substances released during early equine pregnancy appear to interact with the immune system, reducing its response and potentially aiding in the acceptance of the pregnancy.

Study Methodology

• The study was conducted using embryos and endometria (or lining of the womb) collected from mares 14 days after their ovulation.
• These samples were then cultured for 20.5 hours and the impact of their culture supernatant (the liquid containing substances released by cells) on the activity of lymphocytes, a type of white blood cell, was analysed.
• The key method of analysis was to observe the impact on the lymphocyte incorporation of a radioactive compound called [3H]thymidine, which can be used to track DNA synthesis and therefore cell proliferation.

Findings

• Supernatant from the endometrium of nonpregnant mares did not affect lymphocyte activity. However, the supernatant from both the embryo and the endometrium of pregnant mares reduced the degree of lymphocyte proliferation.
• These findings suggest that certain substances only present or secreted during pregnancy interact with the lymphocytes, reducing their activity. The study points out that it could be the end result of a combination of suppressive and stimulating factors.
• In the presence of indomethacin, a nonsteroidal anti-inflammatory drug, immunosuppressive effects were not present in majority of cultures, suggesting that these factors may be affected by this class of drugs.
• Charcoal treatment, trypsin treatment or heat treatment of the supernatants also reduced the suppressive effect on lymphocyte proliferation, indicating the potential classes of substances involved.

Implications

• The research suggests an interplay between the developing foetus/embryo and the maternal immune system, where substances from the former appear to modulate the latter probably helping in maternal acceptance of the pregnancy.
• Identifying these substances could have implications not only for understanding pregnancy in horses, but also for understanding immune system adaptation during pregnancy in general, offering potential insights for human medicine.