IFN-γ was produced by incubation with DC/MIH-2 from CD4 (+) T cells but not from CD8+ T cells of inoculated mice. Anti-IFN-γ antibody attenuated the cytotoxicity of spleen cells. Immunization of CD4 (+) T cells with DCs loaded with homologous HCC cells, which produce IFN-γ in response to HCC antigens, leads to activation of macrophages that kill liver tumor cells at an early stage. This evidence concerns the gene CD4 and hepatocellular carcinoma.