International Journal of Health Studies1120150209Differential Expression of CD16 and CD56 on Natural Killer (NK) Cell Subsets in Multiple Sclerosis and Neuromyelitis Optica181810.6543/ijhs.v1i1.18ENMehdiKhaksariDept. of Physiology, School of Medicine, Shahroud University of Medical Sciences, Shahroud, Iran. email@example.comSayyed HamidZarkesh-EsfahaniMasoudEtemadifarMohsenMasjediRoqayehAliyariMajidRahmati20141208Introduction: Multiple sclerosis (MS) and Neuromyelitis optica (NMO) are inflammatory and demyelinating diseases of the central nervous system (CNS). NK cells are supposed to play an important role in the pathophysiology of MS, but their role in the NMO remains unknown. The aim of this study was to compare the prevalence of different subpopulations of NK cells in the patients with MS and NMO and healthy individuals.Methods: Treatment Naive MS and NMO patients, age, and sex matched controls were included in this study. PBMCs were isolated from peripheral blood and different phenotypes of circulating NK cells were compared with the flow cytometry analysis.Results: There were no significant differences in the mean percentages of circulating NK cells expressing the CD56 bright molecule in patients with MS and NMO. However, the mean percentages of circulating NK cells expressing the CD56bright molecule were significantly lower in all patients groups, compared to controls. In addition, the mean percentages of circulating NK cells expressing the CD16dim molecule was significantly higher in the patients with MS, compared to controls/any other groups. The mean percentages of circulating NK cells expressing the CD56dim molecule were significantly higher in the patients with MS than the controls. There were significant differences in the mean percentages of circulating NK cells expressing the CD16bright molecule between the patients with MS, and NMO/controls.Discussion: The results indicate that evaluation of NK cell subsets has an implication for the biomarker discovery and therapeutic targets in given diseases.