IL-10 as a mediator in the HPA axis and brain

Certain functional interactions between the nervous, endocrine, and immune systems are mediated, by cytokines. The pro-inflammatory cytokines, interle ukin-l (IL-I) and tumor necrosis factor (TNF) were among the first to be re cognized in this regard. A modulator of these cytokines, IL-10, has been sh own to have a wide range of activities in the immune system; in this review , wa describe its production and actions in the hypothalamic-pituitary-adre nal (HPA) axis. IL-10 is produced in pituitary, hypothalamic, and neural ti ssues in addition to lymphocytes. IL-10 enhances corticotropin releasing fa ctor (CRF) and corticotropin (ACTH) production in hypothalamic and pituitar y tissues, respectively. Further downstream in the HPA axis endogenous IL-1 0 has the potential to contribute to regulation of glucocorticosteroid prod uction both tonically and following stressors. Our studies and those of oth ers reviewed here indicate that IL-10 may be an important endogenous regula tor in IIPA axis activity and in CNS pathologies such as multiple sclerosis . Thus, in addition to its more widely recognized role in immunity, IL-10's neuroendocrine activities described here point to its role as an important regulator in communication between the immune and neuroendocrine systems. (C) 1999 Elsevier Science B.V. All rights reserved.