When compared to AC, HAM/TSP patients have higher levels of spontaneous lymphocyte proliferation (Sakai et al. 2001; Pinto et al. 2011) increased HTLV-1 expression, and importantly, a higher frequency of HTLV-1 specific CD8+ T cells (Kubota et al. 2000; Yamano et al. 2002), which are thought to be critical mediators of central nervous system (CNS) injury. The gene discussed is CD8A; the disease is tropical spastic paraparesis.