The observation that neuroendocrine peptide hormones are produced by lymphocytes and that cells of the immune system have specific receptors for neuroendocrine hormones now provides a molecular basis for the interactions between the nervous, endocrine, and immune systems. Our present results detecting the production of immunoreactive growth hormone and growth hormone releasing hormone (irGHRH) from lymphocytes is yet another instance in which the immune system is shown to produce hormones commonly found in the neuroendocrine system. GH and GHRH are of particular interest since they are the hormone link between somatic development and its regulation by the central nervous system. The ultimate goal of this project is to determine the biological significance of leukocyte-derived irGH. The early focus in these studies will be to determine whether lymphocyte GH and GHRH- induced biological effects occur in vivo and in vitro. We believe these studies are highly justified based on our results showing that leukocytes do in fact produce GH and GHRH-like peptides. We also plan to study the factors that stimulate or inhibit the production of leukocyte-derived irGH and determine its immunoregulatory activity. Finally, we are proposing to determine the structure of irGH by determining the differences or similarities in the sequences of GH cDNA in leukocytes versus pituitary cells. We will also determine the cDNA sequence of leukocyte-derived irGHRH and compare the similarities to hypothalamic GHRH. We expect the results of these studies will increase our understanding of immunophysiology and establish the role of irGH and irGHRH within the immune system and in the commonality between the neuroendocrine and immune systems.
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