Expansion of iNKT cells by α-GalCer stimulation decreased the number of HTLV-1–infected T cells in ACs but not in HAM/TSP and ATL patients. (A) PBMCs from ACs (n = 6) and HAM/TSP (n = 11) and ATL patients (n = 5) were cultured with α-GalCer (100 ng/mL), and the percentage of iNKT cells on days 0, 7, 14, and 21 was plotted. (B) PBMCs from ACs (n = 6) and HAM/TSP (n = 11) and ATL patients (n = 4) were cultured for 14 days with or without α-GalCer, and the proviral load in each sample was quantified by real-time PCR. In ACs, the proviral load in PBMCs cultured with α-GalCer was significantly lower than that of cultured PBMCs grown without α-GalCer (P = .047). No significant difference was observed between HAM/TSP (P = .718) and ATL (P = .298) patients. Wilcoxon signed-rank test was used for statistical analysis.