Mu opioid receptor gene expression in immune cells

We have previously demonstrated that administering morphine sulfate to rhesus monkeys alters the cell-mediated as well as humoral immune responses of these primates. Furthermore, morphine treatment greatly reduces the chemotactic and phagocytotic activities of primate polymorphonuclear (PMN) cells. The present study describes the identification and isolation of mRNA encoding the mu opioid receptor gene sequence from human and monkey immune cells. Through the use of primer sequences designed from the human brain mu opioid receptor cDNA sequence, specific opioid receptor segments in mRNA transcripts were amplified, cloned, and sequenced. The mu opioid receptor gene was therefore found expressed in the following cell types: CEM x174 (a hybrid of human T and B cells), Raji (human B cells), human CD4+ cells, human monocytes/macrophages, human PMN, monkey peripheral blood mononuclear cells (PBMC), and monkey PMN. These studies present the first evidence to demonstrate that cells of human and monkey immune systems constitutively express mu opioid receptor mRNA.