Proliferation and cytokine secretion of T cells incubated with NK cells. (A) NK cells isolated from mice vaccinated with DA1-3b/CXCL10 cells (NK/CXCL10) or DA1-3b/IL12 cells (NK/CXCL10) or not vaccinated (NK/naive) were cocultured for 2 weeks with CFSE-labeled mouse CD4⁺ (▪) or CD8⁺ T cells (▦) and analyzed by flow cytometry for percentage of dividing cells. (B) Same procedure as in panel A but the NK cells were from naïve mice and incubated in vitro with 100 ng/mL recombinant mouse CXCL10 for 24 hours before coculture. (C) Human NK cells were incubated with 100 ng/mL recombinant human CXCL10 for 24 hours, then cocultured with CFSE-labeled human CD4⁺ (▪) or CD8⁺ T cells (▦) for 2 weeks and analyzed by flow cytometry for percentage of dividing cells. (D-E) Same procedure as panel A with mouse CD4⁺ (▪) or CD8⁺ T cells (▦) colabeled with CSFE and (D) an anti–IFN-γ or (E) anti–TNF-α antibody. (F) Effect of in vivo blocking of B7-H1 with anti-B7-H1 (colored lines and symbols) or control isotype (black lines and symbols) on overall survival of mice vaccinated with 10⁶ irradiated leukemic cells (•, DA1-3b/CXCL10; ▴, DA1-3b/IL-12; or ▪, DA1-3b/Zeo) and then challenged with 10⁵ wild-type DA1-3b leukemic cells. All experiments were performed in quadruplicate and repeated at least 3 times. Data represent mean and SD.