A blessing and a curse: is high NK cell activity good for health and bad for reproduction?

Few topics in recent reproductive medicine have been the subject of as much controversy, media attention and passionate debate as natural killer (NK) cells and their role in reproductive failure. The question of whether elevated NK cell levels are a cause of infertility and pregnancy loss, and whether they provide a potential target for therapy to improve reproductive outcomes, lacks a definitive answer. It is clear, however, that a significant number of women with reproductive failure have abnormal NK cell parameters reflecting high immunological activity. Amongst all the debate, the wider implications of NK cell overactivity - and attempts to suppress it - have not yet been considered. The literature suggests that although elevated NK cell activity may not be conducive to reproduction, it could in fact be beneficial in other areas of health and disease such as cancer and infection. Further research is needed to determine whether this hypothesis holds true in women with NK cell-related reproductive failure.