Effect of Influenza A Infection on Umbilical Cord Blood Natural Killer Function Regulation With Interleukin-15

Background. Influenza A is a major pathogen of humans and has the potential to cause worldwide pandemics. Natural killer (NK) cells are important effector cells in the innate immune response against viruses, including influenza A. Infants are more susceptible to severe influenza A viral infection, possibly attributed in part to their defective NK function. Methods. We compared the NK responses to influenza using umbilical cord blood (UCB) and adult peripheral blood (APB) mononuclear cells and purified NK cells. Results. Influenza A induced dose-dependent apoptosis of NK cells with down-regulation of NKp46 expression, which was more pronounced in UCB. Both UCB and APB NK cells responded to influenza infection by up-regulating CD69 and CD107a expression, a process further enhanced by interleukin (IL) 15. Influenza exposure also down-regulated perforin expression and K562 cytotoxicity in UCB NK cells, which was partially restored by IL-15. The production of interferon (IFN)c and tumor necrosis factor (TNF)a by NK cells in responding to influenza was further enhanced by IL-15. Conclusions. Our findings show differential NK responses between newborns and adults. IL-15 may be beneficial in combating influenza by enhancing cytotoxic function and IFN-c production.