Surprisingly, the reduced number of Th17 cells in PBMC from HAM/TSP patients combined with the increased frequency of CD4+ T cells with suppressive phenotype (CD39+CD25+) resembles results of our previous studies and from others in HIV-1 infection [50], [82], [84], where we demonstrate that IL-2 mediates expansion of CD4+ T cells expressing CD25, FoxP3, and lacking CD127, with a negative effect over Th17 cells frequency. This evidence concerns the gene ENTPD1 and tropical spastic paraparesis.