Indeed, widespread Fas+ T-cells are colocalized with apoptotic T-cells in active lesions (Umehara et al., 2002) while soluble Fas ligand is increased in CSF of HAM/TSP patients (Saito et al., 1999), suggesting increased Fas-mediated apoptosis of CD4+ T-cells in CNS. This evidence concerns the gene FASLG and tropical spastic paraparesis.