RESUMO
Here, we evaluated the influence of endogenous opioid activation on immune responses by examining consequences of all three opioid receptor gene (mu, delta and kappa) inactivation. In triple-opioid receptor knockout mice, splenocytes and thymocytes numbers, lymphocyte subsets as well as proliferation and cytokines induced by in vitro stimulation of T lymphocytes were measured. Compared with wild-type mice, similar lymphocyte distribution in thymus and spleen as well as comparable T lymphocyte proliferation were observed, while lower levels of IL-2 and IFNγ as well as higher levels of IL-4 and IL-10 were found in triple-opioid receptor knockout mice. Together, our results indicate a shift from TH1 to TH2 cytokines in triple-opioid receptor knockout animals, suggesting that global endogenous opioid tone drives T lymphocytes toward a TH1 profile under non-pathological conditions.