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 CD8α+ 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 ELISA.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 an-tigen was augmented with the CD8α+ DC/T ratio increased(P<0.05).When antigen concentration ≤ 5 μg/mL and CD8α+ 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 cytotoxicity assay showed that when CD8α+ DCs were pulsed with allogeneic tumor antigen,the maximal T cell killing efficiency could reach(100±7.7)%,whereas
