Activation of HTLV-1 Tax induces resistance toward CD95-mediated apoptosis. Jurkat ERtax and ERΔtax cells were incubated with 30 μg/mL anti-CD3, 2μM HT, or both for 24 hours and subsequently stimulated with the indicated concentrations of LZ-CD95L for an additional 16 hours. Apoptosis was determined by FSC/SSC analysis. Specific apoptosis was calculated as described in “Materials and methods.” The experiment shown is representative of 5 independent experiments.