A rapidly growing body of evidence reveals that complex networks of co
mmunication exist between the neuroendocrine and the immune systems. E
ssential to the maintenance and function of the immune-endocrine circu
itry are an array of chemical mediators produced by cells of the immun
e and endocrine systems. Cytokines are glycoproteins (molecular masses
of 15,000-20,000) that are elaborated by antigen-activated immune cel
ls and responsible for orchestrating immune cellular activities. These
inflammatory mediators also affect the functioning of the neuroendocr
ine system. Thus, interleukin-1 (IL-1), IL-2, IL-4, IL-6, tumor necros
is factor-alpha and interferon-gamma affect the secretion of hypothala
mic and anterior pituitary hormones in vitro and in vivo, and specific
high-affinity receptors for IL-1, IL-2, and IL-6 have been identified
in neuroendocrine tissues. A paracrine role for these factors in the
regulation of neuroendocrine function may be advanced because certain
of these mediators (e.g., IL-1, IL-6) are present in the hypothalamus
as well as the anterior and neurointermediate lobes of the pituitary.
The production of these cytokines in neuroendocrine cells is enhanced
by neuropeptides, endotoxin, and other cytokines. We propose that the
local neuroendocrine cytokinergic tone may act in a facilitative manne
r to enhance the secretion of hypothalamic-pituitary hormones. (C) 199
5 Academic Press, Inc.