Neuroendocrine Effects on Immune System

Review
In: Endotext [Internet]. South Dartmouth (MA): MDText.com, Inc.; 2000.
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Excerpt

The immune system is regulated by a variety of factors ‘from within’: regulatory T cell subsets, cytokines, chemokines, complement, antibodies, etc ., and by factors ‘from without’ (a term used by Medawer in 1973): different hormones, neurotransmitters or neuropeptides present in the microenvironment of immunocompetent cells. During an immune response the brain and the immune system “talk to each other” and this process is essential for maintaining homeostasis . Thus, the brain and the immune system are the two major adaptive systems of the body (1-3).

The central nervous system affects the immune system through the neuroendocrine humoral outflow via the pituitary, and through direct neuronal influences via the sympathetic, parasympathetic (cholinergic) and peptidergic/sensory innervation of peripheral tissues. Thus, circulating hormones or locally released neurotransmitters and neuropeptides regulate major immune functions such as antigen presentation, secretion of cytokines and antibodies, selection of T helper (Th)1 or Th2 responses, lymphocyte activity, proliferation and traffic. Alternatively, certain cytokines such as interleukin (IL)-1, IL-6 and tumor necrosis factor (TNF)-, released during an immune response activate the central components of the stress system, alter neurotransmitter networks activity and induce fever, sleepiness, fatigue, loss of appetite and decreased libido. In addition, they activate the hepatic synthesis of acute phase proteins – changes referred to as ‘sickness behavior’ and ‘acute-phase response’, respectively (Figure 1).

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