The NK cell (CD56+) frequency is diminished in HTLV-1 infections and HAM/TSP (Azakami et al., 2009; Tattermusch et al., 2012; Amorim et al., 2019) (Although Some studies do not show a reduced count (Tattermusch et al., 2012; Saeed et al., 2020)) and NKT cells (CD56+/CD3+) demonstrate reduced proliferation when exposed to activation molecules (Azakami et al., 2009). This evidence concerns the gene NCAM1 and tropical spastic paraparesis.