Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 9 2 2010 06 15 69 77 Shiva Saghafi Department of Immunology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran Ali Akbar Pourfathollah Department of Immunology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran Maryam Kheirandish Iranian Blood Transfusion Center, Tehran, Iran Anahita Azimdoust Children Medical Center, Tehran University of Medical Sciences, Tehran, Iran Massoud Behnia Children Medical Center, Tehran University of Medical Sciences, Tehran, Iran Mohammad Shahjahani Department of Immunology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran Mostafa Moin Immunology, Asthma and Allergy Research Institute, Tehran University of Medical Sciences, Tehran, Iran 2015 10 01 Hematopoietic cord blood (CB) stem cell transplantation has more advantages to other cell sources because of lower Graft Versus Host Disease (GVHD). Interleukin-15(IL-15) is an immunoregulatory cytokine, known to enhance cytolytic function of cord Natural Killer (NK) cells. The aim of this study was to investigate the effect of IL-15 on NK cytotoxicity simultaneously in different cell death stages. We compared the ability of IL-15 to enhance the NK cytotoxicity of CB in comparison to adult blood Mononuclear Cells (MNCs) against K562 target cells by co-staining with AnnexinV-FITC and Propidium Iodide after 3.5 h incubation at 37C and 5% CO2 by using flow cytometric method. We also evaluated phenotypic changes after treatment by IL-15 in both cell sources. Our results indicated that CB samples had lower level of apoptosis, while necrosis was negligible; also by escalating Effector: Target (E: T), we got higher level of apoptosis and necrosis in peripheral blood (PB). NK activity of cord and adult MNCs was enhanced by incubation with IL-15 (10 ng/ml) for 72 h with significantly higher results of PB in comparison to CB (p https://ijaai.tums.ac.ir/index.php/ijaai/article/view/271 https://ijaai.tums.ac.ir/index.php/ijaai/article/download/271/271