Aging, exercise, training, and the immune system.

Human immune function undergoes adverse changes with aging, including development of a relative immune deficiency and an immune dysregulated state. The T cells show the largest age-related differences in distribution and function. The antibody production capacity of B cells also shows an age-related decline. Acute bouts of exercise modulate many immune parameters as seen in peripheral blood. With regard to NK cell activity, a single bout of moderate exercise seems to be well tolerated by the elderly, and the resting NK cell activity of elderly subjects seems to increase with training. Cross-sectional comparisons of immune status imply that habitual physical activity may enhance NK cell activity and check certain aspects of the age-related decline in T cell function. Future studies are required to clarify whether such long-term exercise and resulting improvements of immune function give rise to any beneficial effects on infections, malignancies, and autoimmune disorders.