CD8A and tropical spastic paraparesis: However, HAM/TSP patients show extremely high cellular and humoral immune responses such as high frequencies of Tax-specific CD8+ T cells as well as cytomegalovirus (CMV)-specific CD8+ T cells in PBMCs [7], [8], [28]; high antibody titer to HTLV-1 [6]; and increased production of proinflammatory cytokines such as IL-6, IL-12, and IFN-γ [9].