Tumor necrosis factor-α (TNF-α) functions as a two-edged sword in the liver. TNF-α is required for normal hepatocyte proliferation during liver regeneration. It functions both as a comitogen and to induce the transcription factor nuclear factor-κB, which has antiapoptotic effects. On the other hand, TNF-α is the mediator of hepatotoxicity in many animal models, including those involving the toxins concanavalin A and lipopolysaccharide. TNF-α has also been implicated as an important pathogenic mediator in patients with alcoholic liver disease and viral hepatitis.