The role of CD8(+) T cells in multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE) is still unclear. We describe here significantly reduced disease activity of EAE both in Lewis rats depleted of CD8(+) T cells by monoclonal antibodies and CD8 knockout rats, which was accompanied by reduced leukocyte infiltration into the spinal cord. We detected myelin basic protein (MBP)-specific CD4(+) T cells in peripheral lymphoid organs of CD8-depleted animals which, however, failed to differentiate into interferon-γ-producing effector cells. Our results indicate that CD8(+) T cells interact with myelin-specific CD4(+) T cells early in EAE enabling them to differentiate into pathogenic effector cells.