Exercise and Immunity

Summary

The number of leukocytes, neutrophils, and natural killer (NK) cells increases proportionally to exercise intensity immediately after exercise, but the numbers of neutrophils and NK cells are approximately the same as before exercise. However, the number and activity of leukocytes are suppressed and the frequency of respiratory infection is increased after repeated prolonged exercise. Hyperthermia also induces increases in the numbers of leukocytes and NK cells, and cell activity proportionally rises with core temperature, resulting in lower susceptibility to infection. Plasma concentrations of cortisol, catecholamines, and growth hormone increase markedly during and after severe exercise. The decrease in lymphocyte number and immunosuppression after severe exercise may result from an increase in cortisol induced by exercise. The concentrations of interleukin 1 and interleukin 6 in exercise-loaded mice after 2 h after lipopolysaccharide administration were significantly lower than those in the sedentary control group, when mice were primed with Propionibacterium acnes. The longer survival time in the mice that exercised after lipopolysaccharide administration may by induced by a decrease in serum concentrations of interleukin 1 and tumor necrosis factor-α caused by exercise-induced increases in adrenocorticotropic hormone and glucocorticoids because interleukin 1 and tumor necrosis factor-α can accelerate the release of interleukin 6.

Glutamine is utilized as an important nutrient for lymphocytes and macrophages, and plasma glutamine concentrations are usually lower in rats trained by chronic exercise. Thus, it can be said that immunosuppression is in part induced by lower plasma glutamine concentration caused by prolonged training. Chronic fatigue and appetite suppression sometimes occur during excessive training. Decreased food intake due to appetite suppression accompanied by chronic fatigue induces immunosuppression.