Effects of regular exercise on lymphocyte subsets and CD62L after psychological vs. physical stress

To examine the effects of regular physical activity on lymphocyte responses to a speech stressor and an exercise challenge.

We assessed lymphocyte subsets and CD62L expression pre, immediately after and 15 min after a speech task vs. exercise in 24 high vs. 24 low physically active subjects. Catecholamine levels were determined by radioenzymatic assay, and enumeration of cells was assessed by flow cytometry.

Both tasks induced significant increases in plasma epinephrine (EPI; P<.05) and norepinephrine (NE; P<.001) levels. Similarly, both tasks led to increases in the numbers of lymphocyte subsets (P<.05). Physically active individuals showed attenuated responses to the speech stressor in numbers of CD62L(+), CD45RA(+), CD45RO(+) CD8(+), CD45RO(+) T(H) and CD62L(-) natural killer (NK) cells (P's<.05). In contrast, physical activity level had no significant effect on lymphocyte subsets or CD62L expression in response to exercise.

The findings suggest that physical fitness affects immune responses to a psychological but not a physical stressor. It is an interesting but open question whether attenuated lymphocyte trafficking responses to stress in regular exercisers might have clinical implications regarding host defense by the immune system.