Importance of immune deviation toward Th1 in the early immunopathogenesis of human T-lymphotropic virus type I-associated myelopathy

Although the principal neuropathological feature of human T-lymphotropic vi rus type I (HTLV-I)-associated myelopathy (HAM) is chronic inflammation of the spinal cord, characterized by perivascular cuffing of mononuclear cells accompanied by parenchymal lymphocytic infiltration, the precise mechanism s by which HTLV-I infection causes chronic inflammation of the spinal cord are still obscure. In patients with HAM, peripheral blood CD4(+) T lymphocy tes, particularly HTLV-l-infected CD4(+) T lymphocytes, have increased adhe rent activity to endothelial cells and transmigrating activity through base ment membranes. In addition, the profile of cytokine expression suggests in creased numbers of Th1 cells in peripheral blood CD4(+) T lymphocytes of pa tients with HAM. These findings strongly suggest that immune deviation towa rd Th1, which might be based on high viral load of HTLV-I, plays an importa nt role in tissue damage in the central nervous system of patients with HAM . We herein emphasize the importance of activated Th1 cells as the first tr igger in the immunopathogenesis of HAM. (C) 2000 Harcourt Publishers Ltd.