The role of CD8+ T cells and their local interaction with CD4+ T cells in myelin oligodendrocyte glycoprotein35-55-induced experimental autoimmune encephalomyelitis.

T cells have an essential role in the induction of multiple sclerosis and its animal model experimental autoimmune encephalomyelitis (EAE). Although for CD4(+) T cells it is well established that they contribute to the disease, less is known about the role of CD8(+) T cells. Our aim was to determine the individual contribution of CD4(+) and CD8(+) T cells in myelin oligodendrocyte glycoprotein (MOG)35-55-induced EAE. We investigated MOG35-55-activated CD8(+) T cells to clarify their potential to induce or attenuate EAE. We monitored the behavior of CD8(+) T cells and their interaction with CD4(+) T cells directly at the site of inflammation in the CNS using intravital imaging of the brainstem of EAE-affected living anesthetized mice. We found that mice without CD4(+) T cells did not develop relevant clinical signs of disease, although CD8(+) T cells were present in the CNS of these mice. These CD8(+) T cells displayed reduced motility compared with those in the presence of CD4(+) T cells. In mice that harbored CD4(+) and CD8(+) T cells, we saw a similar extent of clinical signs of EAE as in mice with only CD4(+) T cells. Furthermore, the dynamic motility and viability of CD4(+) T cells were not disturbed by CD8(+) T cells in the lesions of these mice. Therefore, we conclude that in MOG35-55-induced EAE, CD8(+) T cell accumulation in the CNS represents instead an epiphenomenon with no impact on clinical disease or on the effects of CD4(+) T cells, the latter being the true inducers of the disease.