Involvement of CD95 in drug-induced apoptosis of resting and activated lymphocytes.

(A) PBLs and stimulated lymphocytes were cultured in medium, cytarabine, and etoposide for 12 hours. CD95 PE fluorescence profiles of CD4⁺CD45RO⁺ T lymphocytes after 12-hour culture in medium (filled curve, dark), 10 μg/mL cytarabine (filled curve, light), and 10 μg/mL etoposide (open curve) are depicted. (B) Unstimulated and stimulated lymphocytes were cultured in medium (black), 10 μg/mL cytarabine (gray), and 10 μg/mL etoposide (white) for 6 and 12 hours and subsequently were cultured with and without apoptosis inducing anti–APO-1 (IgG3) for another 4 hours. Percentages represent specific CD95-mediated cell death of CD4⁺CD45RO⁺ T lymphocytes. Results from a representative experiment of 3 independently performed experiments are shown. (C) Stimulated lymphocytes were cultured with 10 μg/mL etoposide and neutralizing CD95 ligand antibody NOK-2 and CD95 receptor blocking anti–APO-1 Fab for 6 and 12 hours. Percentages represent the proportion of annexin V–positive cells of CD4⁺CD45RO⁺ T lymphocytes. Bars represent the error of the experiment performed in triplicate. Results from a representative experiment of 3 independently performed experiments are shown.