FoxP3 expression and Tax expression. (A) Density plot showing Tax and FoxP3 expression in CD4⁺ cells from a representative AC patient after 18-hour incubation. The dot plot was divided in 2 gates: a indicates total CD4⁺ cells; b, FoxP3⁺Tax⁻CD4⁺ cells. (B) Percentage of CD4⁺ cells that express FoxP3 alone (gate α), FoxP3 and Tax (gate β), and Tax alone (gate γ). The P value was calculated by an unpaired t test (2-tailed). This percentage was measured on 28 ACs and 30 HAM/TSP patients. (C) Classic PCR for one AC and quantification of proviral load in 3 independent HTLV-1–seropositive patients. FoxP3⁺Tax⁻ cells were isolated by cell sorting of the CD4⁺ population (gate b) and compared with the total CD4⁺ cell population (gate a). The data were normalized to the level of beta-actin cDNA, and expressed as Tax copy number per 100 PBMCs.