CD8A and tropical spastic paraparesis: However, HAM/TSP patients show very high cellular and humoral immune responses, such as high proportions of Tax-specific CD8+ T cells, as well as cytomegalovirus (CMV)-specific CD8+ T cells in the PBMCs [14,33]; high antibody titer to HTLV-1 [9]; and increased production of proinflammatory cytokines, such as IL-12 and IFN-γ [60].