In CD4+CD25+CCR4+ T cells, the percentage of IFN-γ-producing cells was low and that of IL-10- and IL-17-producing cells was high in HDs, whereas the percentage of IFN-γ-producing cells was increased and that of IL-10- and IL-17-producing cells was decreased in HAM/TSP patients, confirming the results presented in Figure 4 and Figure 5A. Here, CD4 is linked to tropical spastic paraparesis.