CD4 and tropical spastic paraparesis: Araya et al. clearly demonstrated that IFN-γ-producing CD4+CCR4+ T cells expressing Th1 marker CXCR3 based on the activation of the Th1 master regulator T box transcription factor (T-bet) induced by HTLV-1 tax in cooperation with specificity protein 1 increased in cerebrospinal fluid (CSF) and spinal cord lesions of HAM/TSP patients [9].