TUNEL analysis of the HTLV-I–infected HUT-102 cell line and control cell line CEM treated or not with IFN (1,000 U/mL) and/or As (1 mmol/L) for 72 hours. Histogram analysis was achieved by setting a region for control cells and defining the region for positive TUNEL to include 2% of the normal cells. Statistics of positive TUNEL region are displayed for each histogram.