Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 12 3 2013 09 15 276 280 EN Maryam Izad Department of Immunology, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Mohammad Hossein Harirchian Iranian Neurological Research Center, Imam Khomeini Hospital, Tehran University of Medical Sciences, Tehran, Iran. Hamed Amiri Iranian Neurological Research Center, Imam Khomeini Hospital, Tehran University of Medical Sciences, Tehran, Iran. Farangis Najafi Department of Immunology, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Zahra Ghaflati Department of Immunology, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Zahra Salehi Department of Immunology, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran. 2015 10 16 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. https://ijaai.tums.ac.ir/index.php/ijaai/article/view/502 https://ijaai.tums.ac.ir/index.php/ijaai/article/download/502/538