Frequencies and mean fluorescence intensities of perforin- and granzyme B–positive CD8⁺ T-cell populations in HTLV-1–infected patients. (A) Representative dot plots of PBMCs stained for cytotoxic function markers and costimulatory molecules. PBMCs from patients with HAM/TSP, asymptomatic healthy virus carriers (HVCs), and uninfected healthy controls (HCs) were costained for CD8, CD27, or CD28, and markers associated with cytotoxic function (ie, perforin or granzyme B [GzmB]). Cells in a CD8⁺ lymphocyte gate were analyzed. Representative dot plots from 1 uninfected control and 1 HAM/TSP patient are shown. (B) The frequency and mean fluorescence intensity (MFI) of the perforin-positive CD8⁺ T-cell population and its subpopulations (CD8⁺CD28⁻ and CD8⁺CD27⁻) in patients with HAM/TSP, HVCs, and HCs. (C) Frequency and MFI of the GzmB-positive CD8⁺ T-cell population and its subpopulations (CD8⁺CD28⁻ and CD8⁺CD27⁻) in patients with HAM/TSP, HVCs, and HCs. (D) Frequency and MFI of the perforin-positive CD8⁺ T-cell population and its subpopulations (CD8⁺CD28⁻ and CD8⁺CD27⁻) in proviral load (PVL)–matched patients with HAM/TSP, HVCs, and HCs. (E) The frequency and MFI of the GzmB-positive CD8⁺ T-cell population and its subpopulations (CD8⁺CD28⁻ and CD8⁺CD27⁻) in PVL-matched patients with HAM/TSP, HVCs, and HCs. The frequency of perforin- or GzmB-positive cells is shown as a percentage within each cell subset (CD8⁺, CD8⁺CD28⁻, CD8⁺CD27⁻). Values represent the means plus or minus the standard error (SE). To test for significant differences among the cell populations between 3 different groups of subjects (HAM/TSP, HVCs, and HCs), one-factor ANOVA was done when the variance of each group was equal by Levene test. If the variance of each group was different, the Kruskal-Wallis test was used. For multiple comparisons, we used Sheffe F to analyze statistical difference. Values of P < .05 were considered statistically significant. ***P < .001; **P < .01; *P < .05.