Several mechanisms by which the nervous and immune systems might interact have now been recognized. The nervous system may affect immune function via direct innervation of immune organs and by secretion of hormones from the pituitary and other endocrine organs. Conversely, cells of the immune system may influence nervous system function by secretion of a variety of chemical messengers, among which cytokines are the best recognized. Also, although classically the brain was considered immunologically privileged, it is now recognized that cells of the immune system may be active in the brain, and that this may be an important factor in many central nervous system (CNS) diseases.
Keywords: immune system; nervous system; conditioning; stress; HPA axis; ACTH; CRF; corticosteroid; cytokines; behaviour; noradrenaline; serotonin; tryptophan