CD4 and tropical spastic paraparesis: Consistent with previous reports [33], the frequency of CD4+CD25+ T cells was higher in HAM/TSP patients without anti-HBZ antibody responses than those of ND, but HAM/TSP patients with anti-HBZ antibody responses showed significantly less CD4+CD25+ T cells compared to patients without anti-HBZ antibody responses (Figure 4 Ei).