CTL lysis of the ⁵¹Chromium-labeled targethp B-LCL indicated in the legend. Effector cells were mononuclear cells derived from animal no. J546 at the times indicated on the horizontal axis after transplantation with autologous CD34⁺ PBSC transduced with MFGS-mCD24. This animal was not transplanted with any CD34⁺ PBSC transduced with MFGS-htNGFR. Controls included target autologous hp B-LCL transduced to express htNGFR and allogeneic hp B-LCL (from control animal no. 4664) transduced and selected to express mCD24 or htNGFR. All effector cells were stimulated with autologous hpB-LCL transduced with either mCD24 or htNGFR retrovirus vectors. CTL assays were performed using E:T ratios of 80:1 to 10:1, although the representative data shown in this figure were performed using an E:T ratio of 40:1. The percent lysis of targets indicated on the vertical axis was calculated by the formula given in Materials and Methods.