IFNG and tropical spastic paraparesis: Although the overproduction of IFN-γ in CD4+CD25+CCR4+ T cells of HAM/TSP patients was demonstrated (Figure 4), it was also of interest to determine whether the production of suppressive cytokines such as IL-4 and IL-10 was decreased in these cells because the CD4+CD25+CCR4+ T cells in healthy donors mainly include Th2 and Treg cells [26].