Immunological mechanisms are believed to play an important role in the pathogenesis of T-lymphocyte alveolitis in patients infected with HTLV-I, based on the cytotoxic immune response of CD8+ T cells [10], and the presence of circulating CD8+ cytotoxic T cells specific for the HTLV-I Tax in patients with HAM/TSP [11,12]. This evidence concerns the gene CD8A and tropical spastic paraparesis.