Interactions between the Neuroendocrine and Immune Systems: Common Hormones and Receptors

Abstract

The studies reviewed here support a molecular basis for bidirectional communication between the immune and neuroendocrine systems. The main findings can be summarized as follows: First, cells of the immune system can synthesize biologically active neuroendocrine peptide hormones. Second, immune cells also possess receptors for many of these peptides. Third, these same neuroendocrine hormones can influence immune function; and fourth, lymphokines can influence neuroendocrine tissues. Although recent studies have begun to unravel the biochemistry of bidirectional communication between the immune and neuroendocrine systems, there are still missing parts in this puzzle. Among the important questions that must be resolved are the identification of factors that trigger the synthesis of neuroendocrine hormones by immune cells. Are these events operating similar to or in balance with pituitary cells? Drugs that interfere with either pathway may be useful. Second, it will be of value to understand the factors controlling neuroendocrine hormone receptor expression on immune cells. A better understanding of the spectrum of positive and negative regulatory events for both systems may determine the ultimate behavior of immune and neuroendocrine cells. In addition, since leukocytes can produce hormones and also have receptors for the same hormones (e.g., ACTH and GH), it is possible that these immunocytes may also influence their own function in an autocrine-like fashion. We have postulated that the immune system can serve as a sensory organ for external stimuli that cannot be detected by the nervous system (Blalock 1984). Thus, the immune system recognizes stimuli such as bacteria, viruses or tumors, whereas the nervous system detects classical sensory stimuli. The contribution of extrapituitary sites of hormone production and function may provide new clues to define psychological and/or pathological states in the pathophysiology of infectious diseases and tumors.

The stimuli-specific role of vasopressin in the hypothalamus–pituitary–adrenal axis response to stress

“…In addition to the adrenal cortex (Voisey et al 2003), ACTH receptors are also found on adipocytes (Boston & Cone 1996), skin cells (Kapas et al 1998) and sympathetic ganglia (Nankova et al 1996). Furthermore, it has been proposed that ACTH can also participate in immunmodulation (Weigent & Blalock 1987).…”

Morphine Reciprocally Regulates IL-10 and IL-12 Production by Monocyte-Derived Human Dendritic Cells and Enhances T Cell Activation

“…Endogenous opiates exert immunostimulatory effects (3,4). Helper T cells produce endogenous opioids, and memory T cells within inflammatory tissue are capable of synthesizing and releasing β-endorphins (38)(39)(40).…”

“…There is growing evidence that opioid receptors are expressed by cells of the immune system and that opioids modulate immune responses. In contrast to endogenous opiates that exert immunostimulatory effects (3,4), both the therapeutic and chronic use of morphine compromise the optimal function of the immune system (5). Opiate addicts are prone to infection.…”

Environmental Endocrine Disruption: An Effects Assessment and Analysis

“…The interrelationship of endocrine and immune systems is complex, but research into this area is progressing rapidly (245)(246)(247). The elucidation of this interaction between endocrine and immune systems is made more challenging with the addition of species diversity (e.g., shellfish, fish, birds).…”