CXCL10 and tropical spastic paraparesis: Although anti-HTLV-1 Ab was negative in CSF and the levels of the inflammation marker CXCL10 (IP-10), which is elevated in HAM/TSP patients (48, 49), were not changed before and after infection in intrathecally inoculated CMs (data not shown), immune regulation, including CD8+ T cell depletion and use of the immune evasion route at the time of infection, caused higher PVLs in CMs.