FUNCTIONAL-ROLE AND SEQUENCE-ANALYSIS OF A LYMPHOCYTE ORPHAN OPIOID RECEPTOR

Pharmacological evidence indicates that lymphocytes express opioid rec eptors, but this finding has been questioned. By DNA sequencing of rev erse transcription-polymerase chain reaction products, we have found t hat mouse lymphocytes express mRNA encoding an orphan opioid receptor. These mRNA transcripts were detected in the CD4(+), CD8(+), and CD4(- )CD8- lymphocyte subpopulations. Northern blot analysis confirmed that splenic lymphocytes express a 1.5-kb orphan opioid receptor mRNA. Fif teen bases encoding Tyr(71)-Arg(75) in the first intracellular loop ar e alternatively spliced, suggesting that orphan opioid receptor mRNA e ncodes two receptor subtypes. Treatment of lipopolysaccharide-stimulat ed lymphocytes with orphan opioid receptor antisense oligonucleotides suppressed polyclonal IgG and IgM production by 50%. Our results provi de direct evidence that lymphocytes express an opioid-like receptor ge ne, and suggest that this receptor plays a functional role in immunoco mpetence.