Characterization of humoral and cellular immunity in the central nervous system of HAM/TSP

In HTLV-I-associated myelopathy or tropical spastic paraparesis (HAM/TSP) immunopathological processes in the central nervous system (CNS) have not been clarified. We compared the humoral and cellular immunity within the CNS and in the systemic circulation of 24 patients with HAM/TSP (8 men and 16 women) to 6 asymptomatic HTLV-I carriers, 7 patients with active multiple sclerosis, 6 patients with acute viral encephalitis, and 39 patients with other non-inflammatory neurological diseases. Significant differences were observed between the HAM/TSP patients and one or more of the control groups: HAM/TSP cerebrospinal fluids (CSF) exhibited higher levels of IgG, IgG index, de novo IgG synthesis rate, and beta 2-microglobulin, and also a predominance of CD8+ cells that expressed CD11a and CD45RO but lacked CD28 antigens. Results in the 6 patients with acute viral encephalitis suggested that the CD8+ population in the CSF which is positive for CD28 and CD45RO is important for the elimination of virus from infected CNS tissues. Therefore, potentially cytotoxic T cells of a unique CD8+CD11a+CD45RO+CD28- phenotype may play a key role in the CNS pathogenesis of HAM/TSP.