The graft-versus-tumor (GVT) effect of T cells induced by tumor antigen-pulsed CD8α+ dendritic cells (DCs) in vitro was investigated in this study. Immature CD8c(DCs were prepared from C57BL/6 (H-2b) bone marrow cells by using a cytokine cocktail. On the 3rd day of culture, CD8α+ DCs were pulsed by allogeneic (Balb/c, H-2d) EL9611 leukemia antigen, or RM-1 syngeneic prostate cancer antigen, with the concentration series of 0, 2.5, 5.0, 10.0, 20.0 μg/mL, respectively, then antigen-loaded immature CD8α+ DCs were co-cultured with syngeneic T cells according to the DC/T ratio of 1:1, 2:1 and 4:1. T cell proliferation was measured by MTT assay. Cytokines including interferon gamma (IFN-γ) and interleukin-10 (IL-10) in CD8α+ DCs and T co-culture supernatant were detected by using ELI SA. Cytotoxic effect of antigen-specific T cells was tested by LDH release assay. Conventional mature DCs (mDCs) induced, from C57BL/6 (H-2b) bone marrow cells by using granulocyte-macrophage colony stimulating factor (GM-CSF) and interleukin-4 (IL-4) served as a control. The results showed that the proliferative activity of T cells stimulated by CD8α+ DCs loaded with allogeneic or syngeneic tumor antigen was augmented with the CD8& DC/T ratio increased (P〈0.05). When antigen concentration 〈 5 μg/mL and CD8a+ DC/T ratio 〈 2:1, the ability of CD8α+ DCs to stimulate T cell proliferation was higher than mDC control in allogeneic tumor antigen-pulsed groups (P〈0.05), but not in syngeneic tumor antigen-pulsed groups (P〉0.05). The level of IFN-γ and IL-10 in CD8α+DCs and T cell co-culture supernatant were increased in both allogeneic and syngeneic antigen-pulsed groups (P〈0.05), and the cytokine level was higher in allogeneic antigen-pulsed groups than in syngeneic antigen groups when the CD8α+ DC/T was 1:1 or 2:1 (P〈0.05). There existed a negative correlation between the level of IL-10 and T cell proliferation. T cell cytotoxi