Effects of elevated plasma noradrenaline concentration on the immune system in humans

This study was designed to test the hypothesis that elevated plasma noradre naline concentrations contribute to the exercise-induced modulation of the activity and percentage of the natural killer (NK) cells, and the leucocyte concentration. In a single blind, controlled, cross-over study, eight heal thy men had noradrenaline infused for Ih and achieved plasma noradrenaline concentrations comparable (20-fold increment) to those previously observed in cycle ergometer exercise (75% of maximal oxygen uptake for 1 h). The nor adrenaline infusion increased the unstimulated, the interleukin-2 and inter feron-a stimulated NK cell activity, and the percentage of CD16+ cells. The natural lytic activity per CD16+ cell however, did not change. The concent ration of neutrophils, lymphocytes and CD16+ cells increased during the inf usion. The neutrophil concentration remained elevated 2 h after infusion, a t which time the lymphocyte count was back to normal. These results are com parable with the effects in the exercise model, and it is suggested that th e augmented plasma noradrenaline concentrations, seen during extreme exerci se, may participate in the exercise-induced immune changes.