CTL-mediated killing of DA1-3b cells transfected with B7.1 and/or B7-H1. (A) Sensitivity to CTL-mediated killing of DA1-3b cells transfected with B7.1 and cell sorted for very low (VL), low (L), high (H), or very high (VH) expression. (B) Sensitivity of DA1-3b cells transfected with B7-H1 and cell sorted as described above. (C) Sensitivity of DA1-3b cells transfected with both B7.1 and B7-H1 and cell sorted for very low, low, high, or very high expression level of B7.1, B7-H1, or both genes. (D) Cytotoxic activity against DA1-3b, DA1-3b/d35, and DA1/d365 cells of naive (CD8⁺ CD62L^- CD45R^- CD44^- CD69^-), effector (CD8⁺ CD62L^- CD45R^- CD44⁺ CD69⁺), effector memory (CD8⁺ CD62Llow CCR7^- CD45R⁺ CD44⁺ CD69⁺), and central memory (CD8⁺ CD62L^high CCR7⁺ CD45R⁺ CD44⁺ CD69⁺) T cells with or without blocking antibodies against B7-H1 and/or B7.1. All experiments were performed at 1:1, 5:1, 10:1, 15:1, and 20:1 E/T ratios; only results obtained at 20:1 E/T ratio are presented. (E) The procedure described for panel D was followed but with DA1-3b cells transfected with both B7.1 and B7-H1 as targets. (F) Quantification by ELISA of IL2 produced by CD8 T-cell subsets in presence of DA1-3b, DA1-3b/d35, DA1-3b/d365, and DA1-3b cells transfected with both B7.1 and B7-H1. Error bars indicate standard deviation.