Neuroimmune Regulation in Immunocompetence, Acute Illness, and Healing

摘要

Adaptive immunocompetence is maintained by growth hormone (GH), prolactin (PRL),and vasopressin (VP). Innate or natural immunocompetence depends on cytokines, hor-mones (especially of the hypothalamus—pituitary—adrenal axis), and catecholamines.The acute phase response (APR, or acute febrile illness) is an emergency defense re-action whereby the adaptive, T cell—dependent, immune reactions are suppressed andthe innate immune function is dramatically amplified. Infection and various forms ofinjury induce APR. Cytokines [interleukin (M)-1β, tumor necrosis factor-a, and IL-6]stimulate corticotropin-releasing hormone (CRH) and VP secretion and cause a "sym-pathetic outflow." Colony-stimulating factors activate leukocytes. CRH is a powerfulactivator of the pituitary adrenocortical axis and elevates glucocorticoid (GC) levels.Cytokines, GCs, and catecholamines play fundamental roles in the amplification of nat-ural immune defense mechanisms. VP supports the APR at this stage. However, VPremains active and is elevated for a longer period than is CRH. VP, but not CRH, iselevated during chronic inflammatory diseases. VP controls adaptive immune functionand stimulates adrenocorticotropic hormone (ACTH) and PRL secretion. PRL main-tains the function of the thymus and of the T cell—dependent adaptive immune system.The ACTH—adrenal axis stimulates natural immunity and of suppressor/regulatory Tcells, which suppress the adaptive immune system. VP also has a direct effect on lym-phoid cells, the significance of which remains to be elucidated. It is suggested that VPregulates the process of recovery from acute illness.