The effect of acute exercise on natural killer-cell activity of trained and sedentary human subjects

Abstract

The effect of acute exercise on natural killer (NK) activity and on the distribution of phenotypic characteristics of peripheral blood lymphocytes was examined. Trained and sedentary individuals underwent a standard progressive exercise test on a cycle ergometer using an incremental work load of 15 W (90 kpm), increased every minute. Each subject was encouraged to exercise to exhaustion, and total ventilation and mixed expired O₂ and CO₂ were measured every 30 sec. All subjects reached the “anaerobic” threshold as judged by the deflection of ventilation at a work load nearVO_2max. NK activity against K562 reached maximum levels immediately after exercise, dropped to a low point 120 min later, then slowly came back to preexercise levels within 20 hr. No significant differences were observed between the trained and the sedentary groups. Furthermore, immediately after exercise the proportion of OKT-3+ and OKT-4+ cells was reduced by 29.8±3.6 and 33.6±5.4%, respectively; the percentage Leu-7+ and Leu-11a+ cells was increased by 53.9±1.7 and 57.3±2.9%, respectively. The percentage OKT-8+ cells was not significantly altered. When the percentage binding of effector to target cells was examined, it was highest at 0 min post-exercise (19±6.2%) and lowest at 120 min postexercise (7±3.9%), but the absolute number of NK cells remained unchanged. The source of serum used in the lytic assay had no effect on the NK activity, as fetal calf serum and autologous sera drawn at different time intervals during exercise gave similar results. Epinephrine suppressed and interferon enhanced the NK activity of all cells tested, which indicates that during and after exercise NK cells did not go through a refractory stage. Our results show that, contrary to other lymphocyte subpopulations, NK cells are resistant to the depletive and modulatory effects of acute exercise and the increase in NK activity is not due to an increase in the absolute number of NK cells.