Although few studies have been performed to
 date, recent evidence suggests that the ability of the immune
 system in older individuals to respond to the stress im- posed from a single bout of exercise is maintained with age. The effect of a single bout of exercise on immune function in young (23 2 yr) and elderly (604 yr) subjects showed that in response to exercise the young subjects had a decrease in PHA proliferative capacity (181). Both young and old subjects had an increase in the NK activity in response to exercise (51, 73). IL-1B and TNF-a secretion can be increased the morning after ex ercise without any current changes in mononuclear cell numbers, indicating that the monocytes are activated in relation to eccentric exercise (42)