Vasopressin and immune function

Vasopressin (VP) has emerged in recent years as a very important immunoregulatory peptide of the hypothalamus. VP is capable of maintaining immune function, both innate and adaptive immunity. This is due to the ability of VP to stimulate both the hypothalamus-pituitary-adrenocortical (HPA) axis and also prolactin (PRL). The HPA axis is important for innate immune function, whereas prolactin maintains adaptive immunocompetence. VP also has a direct regulatory effect on lymphocytes which remains to be elucidated. During acute illness (APR) VP secretion is increased along with CRH. In this case CRH is in control of the inflammatory process, and VP has a supportive role. Innate immunity (INIM) is amplified by glucocorticoids (GC) and catecholamines (CAT) whereas adaptive immune (ADIM) function is suppressed. During chronic inflammation CRH is repressed and VP takes over as a primary hypothalamic immunoregulator. At this stage VP gradually restores homeostasis by stimulating both the HPA axis and PRL secretion in balance and hence restores normal immune function and regulates the healing of the organism. In conclusion, the two hypothalamic immunoregulatory peptides, CRH and VP have different functions. CRH plays an important function in acute phase responses, whereas VP supports APR, but it is really the hypothalamic regulator of healing and of physiological immune regulation.