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