Responsiveness of human natural killer cells during acute, incremental exercise up to exhaustion

AbstractEight healthy male subjects performed a cycle ergometer incremental exercise up to exhaustion to study possible relationships between excess CO2 production (CO2-exc) and natural killer (NK) cells, measured in terms of concentration (NKabs) and as a percentage of lymphocytes in peripheral blood (NK%). A parabola-like regression equation with its vertex downwards best fit the relationship between CO2-exc at Wmax and the difference between NK cell measurements at the maximum workload (Wmax) and at the workload corresponding to the anaerobic threshold (WAT). For NK cell concentration, the best equation was NKabs (cells/mm3)=248.8413–0.3105 CO2-exc (ml min-1)+0.0001 CO2-exc2 (ml min-1) (p=0.044). For NK cells expressed as a percentage, the best equation was NK(%)=108.7636–0.1414 CO2-exc (ml min-1)+0.00001 CO2-exc2 (ml min-1) (p=0.032). Thus, the higher was the CO2-exc the lower was the increase in both NK cell measurements at Wmax with respect to the value observed at WAT. However, when CO2-exc reached more elevated values, then the direction of this relationship was inverted. It may be concluded that when strenuous exercise is performed, an anti-inflammatory/performance-preserving event takes place, while recovery towards a pro-inflammatory/anti-infection state tends gradually to re-establish when a subject’s anaerobic power becomes too high.