The activation of memory CD4(+) T cells and CD8(+) T cells in patients with multiple sclerosis.

To reevaluate whether an association exists between the clinical course of multiple sclerosis (MS) and the activation of memory T cells, we investigated the phenotype of T cells in peripheral blood and cerebrospinal fluid (CSF) of patients with MS using five-color flow cytometry. A cross-sectional study with 39 relapsing-remitting MS patients demonstrated that the percentage of CD25(+)CD45RO(+)CD4(+)CD3(+) cells was significantly increased in peripheral blood as well as in CSF of active MS patients compared with inactive MS patients. A longitudinal study with 11 relapsing-remitting MS patients also showed a higher percentage of CD25(+)CD45RO(+)CD4(+)CD3(+) cells in peripheral blood at the phase of exacerbation than during remission. On the other hand, regardless of the disease activity, the percentage of CD25(+)CD45RO(+)CD8(+)CD3(+) cells in peripheral blood was significantly higher in patients with MS than in healthy control subjects. A lower percentage of CD25(+)CD45RO(+)CD8(+)CD3(+) cells in CSF was observed in active MS patients compared with inactive MS patients. These results suggest that the activation of memory CD4(+) T cells is associated with the exacerbation of MS and activation of memory CD8(+) T cells reflects systemic immunological dysregulation in MS patients. Transient as well as continuous activation of T cells by recall antigens may be involved in the disease course of MS.