The KIR genotype influences CTL efficiency, by affecting HLA class I-mediated HTLV-1 immunity [42], and KIRs influence both innate and adaptive immunity (Figure 1) [1,42], however KIR2DL2 gene is associated with an enhancement of the effect of known protective or detrimental HLA class I alleles on PVL and HAM/TSP risk, for multiple HLA-A, -B and -C molecules. Here, HLA-A is linked to tropical spastic paraparesis.