Perforin expression in HTLV-1 Tax– and CMV pp65–specific CD8⁺ T cells in HTLV-1 infection. (A) Left panel: Dot plots of HLA-A*02/Tax11-19 tetramer-PE (x axis) versus CD8-ECD fluorescence within the lymphocyte gate based on forward versus side scatter. Right panel: Histogram of perforin expression (x axis, arbitrary units, log scale) versus cell number (y axis) in gated virus-specific (tetramer-positive) cells. Representative dot plot from one patient with HAM/TSP is shown. (B) The perforin expression in HTLV-1 Tax– and CMV pp65–specific CD8⁺ T cells in HTLV-1–infected patients. Statistical analysis was done as described in the legend for Figure 1. ***P < .001