The functional competence of uterine-derived polymorphonuclear neutrophils (PMN) from mares resistant and susceptible to chronic uterine infection: a sequential migration analysis.

The research investigates the behavior of polymorphonuclear neutrophils (PMNs), a type of white blood cell, derived from the uteruses of horses in response to infection. The study finds a difference in cell migration between horses resistant and those susceptible to chronic uterine infections.

Research Context

• This study is built upon the significance of polymorphonuclear neutrophils (PMNs) in the immune system. They are white blood cells known for their role in defending the body against infections.
• The researchers chose mares (female horses) as their subjects, with a focus on those prone to chronic uterine infections compared to those that are resistant.
• Chronic uterine infections often occur in mares and can have severe implications on their fertility. Hence, understanding the behavior of immune cells in response to this infection could contribute to better reproductive health interventions in livestock animals.

Methodology

• A total of 28 mares were subjected to an infection with the bacterium Streptococcus zooepidemicus.
• The mares were classified into two groups: those resistant to chronic uterine infection (Grade I) and those susceptible to it (Grade III).
• The researchers gathered cell samples from the uterus before infection and at 5, 12, 15, 20 and 25 hours after infection.
• PMNs were obtained from these samples and their migration responsiveness measured using chamber (filter) assay.

Results

• In the group of mares resistant to chronic infections, there was an initial uptick in PMN migration at 12 hours post-infection, followed by a decline in cell migration and concentration from 12 through 25 hours after the infection.
• In contrast, the susceptible group demonstrated early migration dysfunction at 12 hours after infection, then improvements in PMN function at 15 and 25 hours post-infection.
• Most notably, the concentration of PMNs derived from uterine samples remained elevated in susceptible mares from 12 to 25 hours post-infection. This suggests a continuous enlistment of new PMNs from the body’s general circulation.

Conclusion

• The study concluded that the functional ability of PMNs in the uteruses of mares susceptible to chronic infection seems impaired, particularly their capacity to migrate.
• This compromised migration can potentially contribute to the endurance of chronic uterine infections by impeding the immune system’s ability to efficiently respond to infections which might pave the way to chronic endometritis, a long-term inflammation of the uterine lining.