Stimulation and induction of CTLs by DCs pulsed with apoptotic MM bodies versus cell lysates. (A) T cells (2 × 10⁵ cells) from healthy donor PBMCs were incubated for 5 days with irradiated (15 Gy) autologous DCs cocultured with apoptotic U266 bodies (▪), U266 lysate (□), DCs alone (▨), or apoptotic U266 bodies alone (▦) at indicated T cell–to-DC (T/DC) ratios. ³[H]thymidine (1.0 μCi [0.037 MBq]) was added to each well for the last 12 hours of 5-day cultures. Cells were then harvested and radioactivity was counted. Mean cpm of T cells without stimulator was 409 and of DCs only and apoptotic U266 cells only were less than 50. Data shown indicate mean ± SD of triplicate wells and are representative of 3 experiments. Significantly greater proliferation was observed in T cells stimulated with apoptotic U266–pulsed DCs than other stimuli by Mann-Whitney U test (*, P = .02). (B) Cytotoxicity of CTLs against U266 cells was assessed with ⁵¹Cr-release assay. U266 cells (5 × 10³ cells) labeled with ⁵¹Cr were cultured with CTLs induced by stimulation with DCs cocultured with apoptotic U266 bodies (▪), U266 lysate (▴), DCs alone (□), or apoptotic U266 cells alone (▵) at indicated effector-to-target (E/T) ratios in triplicate for 4 hours at 37°C. Supernatants were then harvested and radioactivity was counted. CTLs stimulated with apoptotic U266 bodies showed significantly higher specific lysis than other stimuli. Spontaneous release of target cells was less than 10%. Specific lysis of K562 cells by CTLs stimulated with DCs cocultured with apoptotic U266 bodies was maximum (14.8%) at an E/T ratio of 20:1. Results shown are mean ± SD of triplicate wells and representative of 3 experiments.