Thus, CD4+CD25+CCR4+ T cells with increased proinflammatory function together with a defective Treg compartment [20], [27]–[29] may overcome the regulatory effect of HTLV-1-uninfected Treg cells [45] and at least partly account for the heightened immune response observed in HAM/TSP patients. This evidence concerns the gene CCR4 and tropical spastic paraparesis.