Comparison of P495-specific and nonspecific killing of HLA A2.1⁺ allogeneic BLCLs by CTLs obtained with different antigen-presenting cells. Black bars indicate cytolysis of allogeneic mismatched A2.1⁺ BLCL^pp65. Percentage of specific killing at an E/T ratio of 10:1 was calculated as the percentage killing of BLCL^pp65 minus the percentage killing of BLCL^flu. Open bars indicate cytolysis of BLCL^flu at an E/T ratio of 10:1 for the same assay. Top to bottom: CTLs activated on autologous ER^- PBMCs, autologous BLCLs, AAPC^A2P495, and AAPC^A2pp65. For the 3 donors, CTLs activated on AAPCs showed the lowest nonspecific killing.