Interleukins counteract opioid agonists immunosuppression.

A centrally acting novel analgesic, PM, added to murine lymphocyte cultures abrogated the mitogenic response to Con A, as well as, interleukin 2 production, in a dose-dependent manner. Simultaneous presence of interleukin 1 (IL-1) and interleukin 2 (IL-2) into the cultures counteracted, in a dose-dependent manner, as naloxone does, the immunosuppressive action of PM as well as of Pethidine, a known opioid agonist. These results show that IL-1 and IL-2 together exhibit classical agonist-antagonist opioid receptor interactions and support the hypothesis that these lymphokines might play a role as endogenous opioid receptor antagonists against endogenous opioid agonists.