An immune response is a net result of a myriad set of cellular interactions, each interaction having multiple regulatory points. Although the nature of the regulatory factors is not fully known, the role of genetics, age, nutrition and circadium rhythm in affecting immunocompetence has been described (Rogers et al, 1979). More recently, it has been suggested that psychoneurological components may also be a potential source of immunomodulatory influences (Solomon, 1981; Riley, 1981; Fauman, 1982). Circumstantial evidence collected as a result of measuring the effects of central nervous system lesions, sympathectomy and emotional status on immunity have led to the concept of nerve mediated regulation of immune responses (Solomon, 1981; Riley, 1981; Jankovic and Isakovic, 1973). Whether denoted as “psychoimmunology”, “psychoneuroimmunology” or “neuroimmunomodulation”, the common denominator is the prediction that lymphoid cell function may be modulated as a consequence of the release of neuropeptides within the lymphoid tissue microenvironment. Innervation of lymph nodes, spleen, and thymus have been described in several species. In vitro experimentation have indicated that some neuropeptides can augment or inhibit immune responses (Payan and Goetzl, 1985). While these data suggest that neuroendocrine substances may serve as immunomodulators there are discrepancies in the literature concerning the effects mediated by some neuropeptides.KeywordsVasoactive Intestinal PeptideCentral Nervous System LesionGlucagon ReceptorMouse LymphocyteVasoactive Intestinal Peptide ReceptorThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.