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Excerpt
The aim of this study was to determine whether NK cells are activated by exercise, and if so, whether activation is related to changes in cytotoxic activity. Eight endurance trained (T) and eight sedentary (S) males, 18-29 yr, completed two sessions in balanced order: (1) 60 min cycling at 70% VO2max and (2) control (no exercise). Venous blood was obtained pre-, post- and 1.5 h post- exercise and at corresponding times in the control condition. Total (CD3-/CD 16,56+) and activated(CD3-/CD16,56+/CD69+) NK cell numbers were assessed by flow cytometry and NKCA measured by 51Cr release. All data were adjusted for diurnal variation. Resting CD16,56+/CD69+ cell numbers and percentages did not differ between T and S. CD16,56+ and CD16,56+/CD69+ cell numbers increased significantly post-exercise; CD16,56+ cell number was higher in T compared with S (P< 0.001). Total NKCA increased immediately post- but decreased 1.5 h post-exercise in both T and S (P < 0.001); suppression of NKCA 1.5 h post-exercise was greater in T than S (P < 0.05). When NKCA was calculated per CD16,56+/CD69+ (activated NK) cell, cytotoxic activity was suppressed post-exercise in both T and S (P < 0.05). These data suggest that: (1) CD69+ activated NK cells are recruited into the circulation during prolonged exercise; (2) NKCA by CD69+ NK cells is suppressed immediately post-exercise; (3) NK cell activation does not contribute to the post-exercise elevation of total NKCA; and (4) training status does not influence NK cell activation at rest and after prolonged moderate exercise.
