Dendritic cell (DC)-based tumor vaccine represents a promising approach to the immunotherapy of malignant tumors. We prepared a novel type of DC-based vaccine, stable conjugates of DCs and EL4 cells transduced with cDNA of OVA (E.G7). Immunization with DC-E.G7 conjugates led to generation of T helper (Th) 1 cytokine-producing cells, antigen-specific CD8+T cells, and strong antitumor immunity that is dependent on both CD4+T cells and CD8+T cells. To further increase the potency of the vaccine, interleukin l8-transfected DCs were used to prepare the ILl8DC-E.G7 conjugates. Immunization with such conjugates significantly increased the production of Thl cytokine-producing cells and the number of antigen-specific CD8+T cells, as well as stronger antitumor immunity. Furthermore, the increased Thl cytokine production and stronger antitumor effect were not observed in mice depleted of IFN-γ. These data indicated that DC-tumor cell conjugates are a potent tumor vaccine. Interleukin l8 can be administrated using gene-transfected cells and enhances antitumor immunity, which is mainly mediated by IFN-γ.