TRAIL-induced apoptosis in NK and CD8⁺ T cells. NK and CD8⁺ T cells were stimulated for 1 day (A) or 10 days (B) as reported in “Materials and methods.” Cells were incubated overnight with 1 μg recombinant human TRAIL. TRAIL sensitivity of NK 3.3 cell line is also reported (B). TRAIL chimera indicates TRAIL-R1-Fc + TRAIL-R2-Fc chimera cocktail administered to the cells at the same time of recombinant TRAIL. TRAIL-sensitive Jurkat and HL-60 cell lines served as positive controls.