Apart from generating T-helper (Th) effector responses, dendritic cells (DCs) are capable of initiating tolerance against the inciting antigens. Therefore, successful DC-based immunotherapy against malignant tumors requires an additional strategy to activate antigen-processing DCs. We studied the antitumor immune responses conferred by fusions of DCs and glioma cells in vitro. Fusion cells (FCs) were stimulated with polyriboinosinic polyribocytidylic acid [Poly(I:C)] and/or small interference RNA (siRNA) of IL-10 (IL-10-siRNA). Increased IFN-β expression induced by Poly(I:C) transfection was accompanied by enhanced production of IL-10 and IL-12p70 in the FCs. We also found that the ability of Poly(I:C)-transfected FCs to produce IL-12p70, but not IFN-β, was preserved when endogenous IL-10 was suppressed by IL-10-siRNA. To analyze the antigen-presenting function further, DCs, glioma cells, and peripheral lymphocytes were established from patients newly diagnosed with glioma. In this experiment, peripheral lymphocytes were stimulated with autologous FCs and restimulated with autologous glioma cells. CD4T cells isolated from the stimulated lymphocytes were subjected to the ELISPOT and WST-1 assays, which revealed that the IL-10-siRNA/Poly(I:C)-cotransfected FCs elicit an efficient tumor-specific Th1 response. These findings support the relevance of using Poly(I:C) and IL-10-siRNA in clinical immunotherapy protocols with an FC-based vaccine for patients with malignant glioma as a means of promoting Th1-induced tumor antigen presentation.