Low and high CD8 positive T cells in multiple sclerosis patients.

Cumulating evidence points to a key role for CD8+ T cells in the pathogenesis of multiple sclerosis.CD8 expression level was believed to be present constantly on the surface of human peripheral blood T cells. However, it was shown that peripheral blood lymphocytes may be divided by the level of CD8 expression, into CD8+high and CD8+low T cells. Now it is well established that the CD8low population of CD8+ T cells demonstrates an activated effector phenotype while the CD8+high T cells have been reported to have regulatory function. In this report we used a flow cytometric assay to compare the frequency of these two subsets in multiple sclerosis patients (n=31) with healthy age- and gender-matched controls (n=18). We found that CD8+ T cells and CD8+low T cells significantly increased in secondary progressive (SP) and primary progressive multiple sclerosis (PPMS) patients in comparison to controls (p<0.0002 and p<0.004 respectively) and also RRMS (p<0.005 and p<0.017 respectively). These results demonstrated the role of CD8low T cells in progressive form of multiple sclerosis.