The effect of exercise on natural killer cell activity in young and old subjects

Alterations in immune function have been commonly reported in elderly persons. We have examined the effect of age on the responsiveness of natural killer (NK) cells to in vitro stimulation with recombinant interleukin-2 (rIL-2) and in vivo stimulation with exercise in 17 healthy subjects (8 young and 9 old). The old subjects were found to have NK cell numbers and function that were not significantly different from the young subjects at baseline. They also responded as well as the young subjects to rIL-2 stimulation of NK cells in vitro. In response to maximal bicycle ergometry exercise, there was a marked rise in NK activity in the old (7.52 +/- 1.71 LU/10(6) pre-exercise vs 15.20 +/- 3.27 LU/10(6) post-exercise, p less than .03) and the young (6.29 +/- .48 LU 10(6) vs 14.56 +/- 1.86 LU 10(6), p less than .005) subjects. Lymphocytes bearing the NK marker Leu 11a also rose significantly post-exercise in both old and young subjects. We conclude that healthy elderly subjects increase their NK activity in response to the acute stressor, exercise, at least as effectively as do young subjects.