Apoptosis of CD57⁺CD8⁺ T cells.

(A) CD8⁺CD57⁺ T cells, CD8⁺CD57⁻ T cells, and CD8⁻CD57⁻ lymphocytes were sorted by flow cytometry followed by PHA stimulation (5 μg/mL). Cells were stained for propidium iodide and analyzed 48 hours following stimulation. (B) PBMCs were stimulated for 12 hours using PHA (5 μg/mL) followed by addition of biotinylated substrate for caspase 3 (Z-VK [Biotin] D(OMe)-FMK, 43 μg/mL) for an additional 12 hours. PBMCs then were stained with anti–CD57 FITC, anti–CD69 APC, anti–CD8 PerCP, and strepavidin PE. Plots shown are gated on live CD8⁺CD69⁺ then discriminated based on CD57 expression. This experiment was performed on 3 individuals, and the data trends were identical. Percentages indicate fraction positive for propidium iodide or activated caspase inhibitor.