ABSTRACT
This chapter focuses on three peptides: substance P, vasoactive intestinal peptide, and somatostatin, which appear to modulate immune function in gut-associated lymphoid tissue. Neuropeptide modulation of the immune response is a science in its infancy, but one which promises to yield a greater understanding of the mucosal immune system with relevance to treatment of infections, autoimmunity, and immunodeficiencies. Neuropeptides, hormones, and lymphokines were so named because they were thought to be unique to their respective tissues; each class of peptide was proposed to function only within a well-delineated system. The peptide is synthesized as a high molecular weight prepropeptide; posttranslational processing results in the known tissue forms, somatostatin 28 and somatostatin 14. The mechanism of action of somatostatin in any tissue may depend on the subtype of receptors expressed in that tissue. The peptide was localized to central and peripheral nervous tissue where it was found to be a neurotransmitter, often coreleased with acetylcholine.
