Insufficient inhibition of super CD95L–induced apoptosis by rh sCD95. (A) Jurkat cells and (B) normal activated peripheral T cells were incubated with rh sCD95 (rh-sFas). Abscissa: concentration of rh sCD95 (rh-sFas), ng/mL; ordinate: percent cell loss. ⋄ indicates 1 ng/mL, ▦, 5 ng/mL, and ○, 25 ng/mL super CD95L (FasL) added to cell medium. n = 2; incubation time, 36 hours. (C) Effect of rh sCD95 (rh-sFas) on apoptosis of Jurkat target cells induced by CD95L (FasL)–expressing effector cells. Effector-target ratio, 3:1; abscissa and ordinate same as in panels A and B; n = 6; incubation time, 22 hours. Note: compared with the respective values at 0, 10, or 100 ng/mL, the moderate inhibition of apoptosis by 1000 ng/mL rh sCD95 (rh-sFas) is significant if all experiments (A-C) are included into the calculation (in each series cell loss is lowest when 1000 ng/mL rh sCD95 [rh-sFas] was added). P < .016, sign-test. (D) Apoptosis of transduced, permanently sCD95 (sFas)–secreting Jurkat target cells after incubation with CD95L (FasL)–expressing effector cells. Effector-target ratio, 3:1; ordinate same as in panel A; incubation time, 22 hours; n = 6. Vectors used: MFG-S-GFP, left column; MFG-S–sFas (sCD95)–IRES-GFP, right column. Cells used 1 week after transduction. (E) Respective amounts of CD95 (sFas) produced by the transduced cells in 48 hours.