Influence of administration of ovarian steroids on the function of neutrophils isolated from the blood and uterus of ovariectomized mares.

The research investigates how ovarian steroids alter functions of blood and uterine neutrophils in mares. It mainly puts a spotlight on the significant reduction in both the blood neutrophils’ migration and uterine neutrophils’ phagocytosis caused by progesterone treatment.

Study Design

• The research focuses on ovariectomized mares, meaning their ovaries have been surgically removed, to examine the effects of ovarian steroids.
• The mares are treated with two types of ovarian steroids, progesterone and oestradiol, followed by an intrauterine infusion of Streptococcus zooepidemicus bacteria 18 hours post-treatment.

Observations on Neutrophils

• The study presents two key observations about neutrophils, which are white blood cells vital for immune function: their ability to migrate and to phagocytose (engulf and digest foreign substances).
• Progesterone treatment appeared to reduce the migration of blood neutrophils in comparison to those from oestradiol-treated and control mares.
• The same reduction was observed when progesterone was added to the blood neutrophils from acyclic ponies in vitro.
• However, uterine neutrophils did not showcase any migration under agarose, which is likely a result of bacterial phagocytosis taking place.

Effects on Phagocytosis

• The hormone treatment, particularly progesterone, had little effect on the phagocytosis of yeast blastospores by the blood neutrophils, but significantly affected the uterine neutrophils.
• Phagocytosis by uterine neutrophils in mares treated with oestradiol and those in the control group, was significantly higher than that by the blood neutrophils.
• In the case of mares treated with progesterone, however, phagocytosis by uterine neutrophils was significantly lower than the other two groups and was similar to that measured in blood neutrophils.

Key Conclusion

• The study concludes that progesterone has a significant impact on reducing both the migration of blood neutrophils and phagocytosis by uterine neutrophils.
• This finding highlights the potential influence of hormone control over the immune response, particularly in reproduction and uterine health, in mares.