The β-cells in the pancreatic islets of Langerhans are the targets of autoreactive T-cells and are destroyed in type 1 diabetes. Macrophage-derived interleukin-lβ (IL-1β) is important in eliciting β-cell dysfunction and initiating β-cell damage in response to microenvironmental changes within islets. In particular, IL-1β can impair glucose-stimulated insulin production in β-cells in vitro and can sensitize them to Fas (CD95)/FasL- triggered apoptosis. In this report, we have examined the ability to block the detrimental effects of IL-1β by genetically modifying islets by adenoviral gene transfer to express the IL-1 receptor antagonist protein. We demonstrate that adenoviral gene delivery of the cDNA encoding the interleukin-1 receptor antagonist protein (IL-1Ra) to cultured islets results in protection of human islets in vitro against IL-lβ-induced nitric oxide formation, impairment in glucose-stimulated insulin production, and Fas- triggered apoptosis activation. Our results further support the hypothesis that IL-1β antagonism in in situ may prevent intra-islet proinsulitic inflammatory events and may allow for an in vivo gene therapy strategy to prevent insulitis and the consequent pathogenesis of diabetes.