BOTH T-CELLS AND MACROPHAGES ARE TARGETS OF KAPPA-OPIOID-INDUCED IMMUNOSUPPRESSION

We have previously shown that antibody responses are inhibited followi ng administration of kappa-opioid agonists. We found that the inhibiti on was blocked by either naloxone or the kappa-selective antagonist no rbinaltorphimine. This inhibitory activity is apparent after short-ter m treatment with the kappa-opioid agonist. In an attempt to identify t he cell populations which serve as the target for this immunosuppressi ve effect, we have carried out cell fractionation analyses to generate isolated T cells and macrophages. Using multiple cell fractionation m ethods, we have determined that short-term treatment of either T cells or macrophages with the kappa-opioid agonist U50,488H results in sign ificant inhibition of in vitro antibody responses. We also find that t he inhibition of both T cell and macrophage activity can be blocked by naloxone. These studies demonstrate that resting T cells and macropha ges express kappa-opioid receptors and exhibit significant opioid resp onsiveness prior to activation by antigen. (C) 1994 Academic Press, In c.