Reproductive Outcomes and General Health in Women with High Natural Killer Cell Levels

Objective: The role of natural killer (NK) cells in reproductive failure has been investigated extensively, but the topic remains controversial and poorly understood. NK cells are known to play an important protective role in cancer and infection, but the implications of high NK cell levels have not been studied with respect to these diseases. This study aimed to identify any differences in reproductive outcomes as well as general health and disease between women with high and normal NK cell parameters. Materials and Methods: 258 female patients at a fertility clinic who received peripheral blood NK cell testing were divided into groups based on their NK cell levels. Their medical history was analysed with regard to fertility, neoplasia, autoimmune disease, atopic disease, gynaecological disorders and mental illness. Results: Women with high NK cell levels had a significantly higher number of embryo transfer procedures (p < 0.05) and lower number of live births (p < 0.05) than women with normal levels. They also trended to having longer periods of infertility and more miscarriages. Higher NK levels were associated with an increased incidence of autoimmune thyroid disease, endometriosis, asthma and positive autoantibody assays, and a reduced incidence of cervical intraepithelial neoplasia, depression and allergy. Conclusions: This study shows that women with elevated NK cell levels have significantly worse reproductive outcomes than those with normal levels. They also appear to have an altered risk of various other diseases. The trends we observed should be targeted in larger, longerterm studies.