CXCL8 and tropical spastic paraparesis: In an attempt to correlate each cytokine value with each other (Figure 2), a positive correlation (p = 0.0013; r2 = 0.3965) between TNF-β and IFN-γ was observed in the asymptomatic group, whereas TNF-α and IL-6 (p = 0.0162; r2 = 0.3944) as well as IL-10 and IL-8 (p = 0.0207; r2 = 0.3476) displayed positive correlations in the HAM/TSP group.