NF-kappa B regulates inflammatory and immune response by increasing the expression of specific genes. In celiac disease proinflammatory cytokines, adhesion molecules, and enzymes whose gene expression is known to be regulated by NF-kappa B are involved. This study investigated the activation of NF-kappa B in inflamed mucosa from patients with untreated celiac disease. Biopsy specimens from control, untreated, and treated patients were subjected to molecular biology analysis. NF-kappa B activation was evaluated by electrophoretic mobility shift assay. NF-kappa B related subunit protein level, and inducible nitric oxide synthase and cyclo-oxygenase 2 protein expression was analyzed by western blot. Both NF-kappa B/DNA binding activity and p50/p65 nuclear levels were higher in biopsy specimens from untreated patients than in those from treated patients and controls. The degradation of I kappa B beta in the cytosol and the reappearance in the nucleus indicated a persistent NF-kappa B activation in celiac disease. NF-kappa B activity was maintained in cultured biopsy specimens up to 6 h and decreased at 24 h, and then the addition of peptic-tryptic digest of gliadin caused the recovery of NF-kappa B activity at 6 h. NF-kappa B/DNA binding activity was correlated with inducible nitric oxide synthase and cyclo-oxygenase-2 protein expression. These results show for the first time that NF-kappa B is activated in the inflamed mucosa of celiac patients and suggest that it may represent a molecular target for the modulation of inflammatory response in celiac disease.