Enkephalin receptors and receptor-mediated signal transduction in culturedhuman lymphocytes

Enkephalins are opioid peptides that bridge the neuroendocrine and immune s ystems. Using how cytometry and a fluorescein conjugate of the endogenous p entapeptide methionine-enkephalin (ME), we have identified enkephalin recep tors on cultured human lymphocytes. Cell surface recognition sites that bou nd ME with high affinity and specificity were detected for NALM 6 (pre-B ac ute lymphoblastic leukemia) and Jurkat (T lymphoma) cells. Brain-like enkep halin receptors were measured for these lymphocytes using conventional radi oligand-receptor assays and the highly delta opioid receptor-selective enke phalin analog [H-3]DPDPE. Upon activation, the lymphocyte enkephalin recept ors transmitted signals that enhanced the accumulation of intracellular cAM P. These studies provide evidence that cultured human lymphocytes of the B (NALM 6 cells) and T (Jurkat cells) lineages express functional enkephalin receptors and suggest that such receptors may be instrumental in the lympho cyte response to opioid peptides and alkaloids. (C) 1999 Academic Press.