Morphine induces CD4⁺ T cell IL-4 expression through an adenylyl cyclase mechanism independent of the protein kinase A pathway

Impaired host defense mechanisms after major operative procedures and trauma are recognized as important factors in the development of infectious complication. Trauma is associated with impaired cellular immunity and CD4 ⁺ T cell Th2 differentiation. We have previously implicated morphine treatment as a possible mechanism for Th2 differentiation after injury. In this investigation we first establish that morphine treatment in vivo results in Th2 differentiation and that this effect is mediated through a naltrexone-sensitive opioid receptor. We investigated the intracellular mechanism by which morphine controls CD4⁺ T cell differentiation and demonstrate that morphine treatment in vitro 1) increases anti CD3/CD28 Ab-induced CD4⁺ T cell IL-4 protein synthesis, IL-4 mRNA, and GATA-3 mRNA accumulation through a pertussis toxin-sensitive receptor; 2) results in a dose-dependent increase in anti-CD3/CD28 Ab-induced CD4⁺ T cell cytoplasmic cAMP concentration; and 3) increases the forskolin-stimulated cytoplasmic cAMP level through a pertussis toxin-sensitive receptor. We also demonstrate that chronic morphine treatment increases anti-CD3/CD28 Ab-induced IL-4 promoter activity and IL-4 immunoprotein expression through a p38 MAPK-dependent, but protein kinase A- and Erk1/Erk2-independent, mechanism.