Two antagonistic subsets involved in the pathway of tolerance and immunity, regulatory CD4+ T cells (Treg) and Th17 cells, derives from a common progenitor [40] and conflicting results regarding frequency and function are found in studies of Tregs and Th17 in the development of HAM/TSP [39], [41], [42], [43], [44], [45]. This evidence concerns the gene CD4 and tropical spastic paraparesis.