CXCL10 and tropical spastic paraparesis: The cut-off concentrations of neopterin and CXCL10 in HAM/TSP patients compared to HTLV-I infected non-HAM subjects are less than 5 pmol/mL and 200 pg/ml, respectively, and the CXCL10 (IP-10) concentration in the CSF of HAM patients with rapid progression is usually more than 5,000 pg/mL (Yamono, Y., personal communication).