Neuroendocrine peptide receptors on cells of the immune system.

The functional role of neuropeptide receptors in the immune system seems to be sensory and regulatory. Signaling molecules (i.e. neuropeptides/neurotransmitters) secreted by immune or neuroendocrine cells can interact with specificity to immunocyte membrane bound neuroendocrine peptide receptors resulting in changes in immune homeostasis. At the onset of this review, three criteria were established in order to formally define the existence of a receptor including the pharmacologic, biochemical, and biological profiles. Applying these criteria, at least ten neuroendocrine peptide/peptide neurotransmitter receptors have met the requirements (table 1). Perhaps more striking, many of these receptors have characteristics which are nearly identical to those receptors found on neuroendocrine tissue. This observation implies irregularities in the physiology of a receptor system in one tissue compartment (neuroendocrine or immune) may be mirrored by the receptors found in the other compartment (neuroendocrine or immune) as well. This rather hypothetical concept is, in fact, supported by data studying ACTH, CRH, and TRH receptors on immune cells relative to the expression or function of these receptors in neuroendocrine tissue taken from patients with neuroendocrine disorders. It is likely that future work will use this relationship to further study the dynamic interaction between the immune and neuroendocrine systems in defining neurologic, neuroendocrine, and autoimmune disorders.