Increased natural killer-cell activity is associated with infertile women

PROBLEM: An increase in natural killer (NK)-cell activity has been observed in women with unexplained recurrent miscarriages. Because of the many similarities between infertility and early pregnancy loss patients, we investigated whether infertile women had raised NK-cell activity. METHOD OF STUDY: We tested 94 infertile women who, in spite of treatment, were unable to conceive for 6 or more months. NK-cell activity was measured by using a chromium-51 release cytotoxicity assay, with K562 human myeloid leukemia cells as targets. RESULTS: NK-cell activity of the infertile group (mean +/- SD; 40.2% +/- 14.7) was significantly higher than the control group (31.5% +/- 11.9, P < 0.0001). The increased NK-cell activity was not associated with age, infertile duration, depression scores, treated hyperprolactinemia, or treated endometriosis. CONCLUSIONS: In certain patients, elevated NK-cell activity may be considered an independent risk factor for infertility.