Natural immunity, including that of the natural killer (NK) cells, is strongly influenced
by physical exercise, but the physiological significance of the reported changes in
NK cells after exercise training is as yet unclear. The exercise effect is likely
mediated by interactions between the central nervous and endocrine systems. Chronic
activation of endogenous opioid systems augments natural cytotoxicity. We have investigated
the possible involvement of opioids in the exercise-induced enhancement of NK cell
function. The pathways by which the central nervous system may communicate with the
periphery include neuroendocrine outflow via the hypothalamic-pituitary-adrenal axis and the autonomic nervous system (ANS) through
direct nerve fiber connections with cells or the organs of the immune system. This
review will discuss the role of various neuroendocrine factors such as growth hormone,
catecholamines and glucocorticoids and the role of the ANS, in particular the sympathetic
division, in modulating NK cell function in response to exercise.
Catecholamines, endogenous opioids, exercise, HPA-axis, NK cells.