Effects of exercise stress on various immune functions in horses.

This study explored how a single strenuous exercise session impacts various immune functions in horses, finding that such exercise can temporarily weaken certain aspects of the horse’s immune system, specifically relating to neutrophil antimicrobial functions and nonspecific defense mechanisms.

Study Design and Measures

In this research, horses underwent a single session of intense exercise. Various immune functions were then observed to determine the effect of this exercise on the animal’s immunity. The metrics involved in this investigation included:

• Chemotactic locomotion and chemiluminescence of neutrophils: This refers to the movement and light-producing reactions of neutrophils, a type of white blood cell essential in combating bacterial infections.
• Measurement of lymphocyte blastogenesis induced by a mitogen: This involves studying the response of lymphocytes, which play a role in the body’s specific immune response, to a substance that encourages cell division and proliferation.
• Quantification of serum cortisol and immunoglobulin: Cortisol, a steroid hormone, is a marker of stress, while immunoglobulins are antibodies generated by the immune system to combat antigens.
• Leukocyte counts: These are a measure of white blood cells, which are crucial to the immune system.

Findings of the Research

After the strenuous exercise, it was observed that:

• The serum cortisol concentration significantly increased, suggesting the session was a stress-inducing event for the horses.
• The neutrophil-to-lymphocyte ratio also significantly increased, further indicating that the exercise was a stressor.
• The chemotactic index and the peak production of chemiluminescence decreased significantly one day after the exercise, suggesting that neutrophil function was hindered by the exercise stress.
• There were no noticeable changes in the proliferation of lymphocytes in response to a mitogen nor in the levels of immunoglobulins, indicating that these aspects of specific immunity were not affected by the exercise.

Conclusion from the Study

The results of this study suggest that a single strenuous exercise session has the potential to temporarily weaken certain parts of a horse’s immune system. Specifically, the exercise negatively affected the horse’s neutrophils’ antimicrobial functions and nonspecific defense mechanisms. However, it didn’t appear to impact the horse’s specific immunity, as the exercise didn’t induce changes in lymphocyte proliferation or immunoglobulin levels.