Effect of exercise on the immune response of young and old horses.

The research investigates the differing effects of exercise on the immune response of young and old horses. The study found that although older horses demonstrated lower immune responses than younger horses, they were more resistant to exercise-induced changes in immune function.

Methodology

The study was conducted on twelve horses – six young and six older ones – all of which had been previously vaccinated against equine influenza virus. A series of assessments were conducted to evaluate the horses’ immune response before and after exercise:

• Venous blood samples were drawn for immunologic monitoring, as well as establishing base values for plasma lactate and cortisol concentrations.
• Mononuclear cells were assayed to ascertain lymphoproliferative responses.
• The same cells were exposed to Interleukin-2 (IL-2) to observe their development into lymphokine-activated killer (LAK) cells.
• Antibodies for the equine influenza virus present in the horses were measured.

Results

Study results were significantly different between young and old horses:

• Prior to exercise, older horses displayed significantly lower proliferative responses to mitogens (substances that induce cell division) than younger ones.
• Exercise had an impact on the lymphoproliferative responses of younger horses, which decreased. However, it didn’t have the same effect on older horses.
• The activity of LAK cells in younger horses increased mildly with exercise intensity.
• Cortisol concentrations in both groups increased post-exercise, but younger horses displayed significantly higher concentrations after exercise at heart rates of 180 and 200 beats per minute as compared to older horses.
• Plasma lactate levels (a form of lactic acid that builds up during strenuous exercise) increased in all horses with exercise intensity. There were no observable differences between the two age groups.
• Older horses had lower antibody titers (measure of antibodies in the blood) against equine influenza virus than younger ones, but exercise did not modify these titers.

Conclusions

Despite lower immune responses, older horses resisted exercise-induced immune function alterations better than their younger counterparts. This could be due to their lower cortisol concentrations. The study reveals the link between stress, aging, and immune function, setting the groundwork for future exploration into age-related immunity adjustments and therapeutic interventions.