IMMUNOBIOLOGY Activated Dendritic Cells From Bone Marrow Cells of Mice Receiving Cytokine-Expressing Tumor Cells Are Associated With the Enhanced Survival of Mice Bearing Syngeneic Tumors

Dendritic cells (DCs), which phagocytose antigens and subse-quently proliferate and migrate, may be the most powerful antigen-presenting cells that activate naive T cells. To deter-mine their role in the immune response to tumors, we used WEHI-3B murine leukemia cells transduced with adenovirus vectors expressing cytokines. We found that mixtures of irradiated cells expressing granulocyte-macrophage colony-stimulating factor (GM-CSF) plus those expressing interleu-kin-4 (IL-4) or tumor necrosis factor a (TNFa) protected mice against WEHI-3B–induced leukemias. When bone marrow mononuclear cells (BMMNCs) obtained from mice that had been injected with irradiated, cytokine-expressing tumor cells were injected into tumor-bearing mice, the survival of the latter was significantly prolonged; the longest survival was observed in mice receiving BMMNCs containing a