Immunoreactive growth hormone (GH) secretion by human lymphocytes: augmented release by exogenous GH

Peripheral blood mononuclear cells (PBMCs) from normal adults secreted small amounts of human growth hormone (GH; 0.2-0.6 pg/10(5) cells/7 days culture) as measured by a highly sensitive enzyme immunoassay. Stimulation of PBMCs with phytohemagglutinin (PHA) consistently showed a 4-6 fold increase in GH secretion. Transformed B-lymphocytes by Epstein-Barr virus also secreted GH (0.8-4.8 pg/5 x 10(4) cells/7 days culture). GH secreted by lymphocytes comigrated with pituitary GH on an Ultrogel AcA44 column. Addition of GH during the culture augmented endogenous GH secretion from PHA-stimulated PBMCs. GH-releasing hormone and a somatostatin analogue, SMS 201-995, did not affect GH secretion from non-stimulated and PHA-stimulated PBMCs. These findings suggest that both T and B lymphocytes secrete immunoreactive GH in a different manner from that in the anterior pituitary.