Moreover, while the frequency of cells expressing TNF and the intensity of expression of TNF was similar in CD4+ T cells from HTLV-1 carriers and patients with HAM/TSP, there was higher frequency of CD8+ T cells expression TNF in HAM/TSP than in HTLV-1 carriers suggesting the participation of TNF in the pathogenesis of HAM/TSP. Here, CD4 is linked to tropical spastic paraparesis.