siRNA4⁺ EBV-CTLs retain proliferative activity in the presence of FK506. (A) The thymidine uptake of NT, irr-siRNA⁺, and siRNA4⁺ EBV-CTLs after stimulation with autologous EBV-LCLs in the presence of increasing concentration of FK506. In the presence of FK506, proliferation of both NT and irr-siRNA⁺ EBV-CTLs is significantly reduced compared with siRNA4⁺ EBV-CTLs. (B) The percentage inhibition for NT, irr-siRNA⁺, and siRNA4⁺ EBV-CTLs grown in the presence of FK506. Bars represent mean ± SD of 4 CTL lines. (C) The expansion in cell numbers of NT, irr-siRNA⁺, and siRNA4⁺ EBV-CTLs stimulated weekly with EBV-LCLs and IL-2 (20 U/mL) with or without the addition of FK506 (5 ng/mL). T-cell numbers increased for all CTLs in the absence of FK506, but in the presence of FK506 increased only for siRNA4⁺ CTLs. Shown are median ± SEM for 6 CTL lines.