Cytotoxicity of Human Cord Blood Natural Killer Cells is Enhanced by Recombinant Interleukin-15

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<0.0001). moreover, il-15 increased the percentage of cd3-/cd56+ and cd25+ cells after 72 h incubation. results showed incubation with human recombinant (hr) il-15 for 3 days increased nk activity. taken together, these results indicated that nk cytotoxicity of cb mncs could be augmented by human recombinant (hr) il-15, but this activity did not reach to same level of pb counterparts. we established that cd25 expression on cb mncs could be increased with il-15, in 72-hour cultures, but to a lesser degree compared to that on corresponding adult pb mncs.