HAM/TSP patients have high frequency of HTLV-1-infected T cells, heightened viral gene expression (in particular, the expression of the viral transactivating gene tax), and virus-specific immune responses, including increased production of proinflammatory cytokines such as IL-6, IL-12, and IFN-γ [7]–[9]. The gene discussed is IFNG; the disease is tropical spastic paraparesis.