Induction of apoptosis in vitro by FASL and drugs. (A) Expression of FAS on PHA-expanded V_δ1 (gray line) and αβ (black line) T-cell lines from healthy donors, compared with an isotype control (dashed line) and measured by flow cytometry. (B) The percentage of early apoptotic cells (annexin-V⁺ propidium iodide [PI]⁻) and late apoptotic cells (annexin-V⁺ PI⁺) in cultures of PHA-expanded V_δ1 (upper quadrants) and αβ (lower quadrants) T-cell lines from healthy donors when either untreated or following incubation with the indicated amounts of rapamycin, pyrimethamine, or sFASL for 4 hours. (C) Percentage fluorescence intensities (after incubation with AlamarBlue reagent) of PHA-expanded V_δ1 (empty circles) and αβ (filled circles) T-cell lines from healthy donors following exposure to the indicated amounts of rapamycin, pyrimethamine, sFASL, or methylprednisolone. The percentage fluorescence intensity was calculated as follows: (fluorescence of treated wells/fluorescence of untreated wells) × 100. Error bars indicate the standard deviation for 3 repeats. These data are representative of at least 2 repeats.