The proportion of circulating mature NK cells (CD56+ CD16+) is decreased in patients with TSP/HAM (Wu et al., 2000; Brito-Melo et al., 2002; Ndhlovu et al., 2009) and other innate immune cells (NKT) are decreased during TSP/HAM as well. Here, NCAM1 is linked to tropical spastic paraparesis.