CENTRAL STIMULATION OF HORMONE-RELEASE AND THE PROLIFERATIVE RESPONSEOF LYMPHOCYTES IN HUMANS

The central nervous system (CNS) may communicate with the immune syste m by direct innervation of lymphoid organs and/or by neurotransmitters and changes in neuroendocrine functioning and hormone release. The co nsequences of selective transient changes in circulating hormones on i mmune functioning in humans have not yet been studied. To address this problem, the authors evaluated the lymphoproliferative responses to o ptimal and suboptimal concentrations of phytohemagglutinin (PHA) and p okeweed mitogen (PWM) under selective enhancement of circulating growt h hormone, prolactin, or norepinephrine. The authors failed to demonst rate any effect of elevated growth hormone levels after clonidine chal lenge on the lymphoproliferative response to mitogens. Similarly, the results did not show any effect of elevated prolactin concentrations i nduced by domperidone administration on the immune test. Exposure of v olunteers to cold resulted in elevation of plasma norepinephrine level s without changes in growth hormone, epinephrine, or cortisol secretio n. Cold exposure induced elevation of plasma norepinephrine and reduct ion of the lymphoproliferative response to the suboptimal dosage of PH A. The reduction was significant 180 and 240 min after exposure. These results are indicative of a relationship between norepinephrine and i mmunity.