FasL is upregulated in an HIV-specific CTL line after PMA exposure, but not after exposure to antigen. Surface expression of fasL was evaluated in a representative gag-specific CTL line from stage A2 HIV-seropositive subject 606 by flow cytometry after overnight culture and stimulation with unpulsed (C) or cognate peptide pulsed (D) autologous BLCL or 10 ng/mL PMA (E) in the presence of metalloprotease inhibitor KB8301. (A) and (B) depict the negative and positive control cell lines for fasL expression (A:BLCL, B:YT Indy). The unshaded histograms represent control antibody stained cells; the shaded histograms, cells stained for fasL. The percentage of fasL-expressing cells is indicated. (F) RT-PCR analysis of FasL expression by HIV-specific CTL clone 352-env52 after stimulation with antigen or PMA. The CTL clone was incubated for 6 hours with autologous lacZ- or HIV-vaccinia infected BLCL at an E:T ratio of 10:1 or with 10 ng/mL PMA. Total RNA was extracted and reverse transcribed. cDNAs amplified with fasL and β-actin primers were electrophoresed and visualized by SyBer Green staining.