Cytolytic response of unstimulated and activated allogeneic and autologous T cells as assessed in a standard 4-hour chromium release assay. A total of 2.5 × 10³ B-CLL cells (◊), CD40-CLL cells (▪), and NK-sensitive K562 cells (▴) were placed in 96-well v-bottom plates and T cells were added at E:T ratios of 3:1, 10:1, and 30:1 in a final volume of 200 μL. Cytolytic response was expressed as the percentage specific lysis. (A) Cytolytic response of unstimulated T cells and (B) cytolytic response of T cells restimulated three times with CD40-CLL cells in an allogeneic setting. (C) Cytolytic response of unstimulated T cells and (D) cytolytic response of T cells restimulated three times with CD40-CLL cells in an autologous setting (patient no. 12). The results are representative for three independent experiments in the allogeneic system and three independent experiments in the autologous system.