Detailed analysis of peripheral blood natural killer cells in women with repeated IVF failure.

PROBLEM To analyse the peripheral blood NK cells in women with repeated IVF failure (RIF) and a fertile control group to determine which parameters best differentiate the two populations. METHODS Peripheral blood from the luteal phase of 171 women with RIF and 33 fertile controls was analysed by four-colour flow cytometry for NK cell concentration, subset differentiation and the activation marker CD69. RESULTS Women with RIF had significantly increased NK cell numbers as determined by concentration (P < 0.05) and percentage of lymphocytes (P < 0.001), increased concentration of the CD56(dim) subtype (P < 0.05), and increased concentration of activated CD56(dim) CD69(+) cells (P = 0.0001). There was no correlation between any NK cell parameters with the length of infertility or number of embryo transfer cycles. CONCLUSIONS Peripheral blood NK cell activity is significantly higher in women with RIF than in fertile controls. Future trials of immune therapy in women undergoing IVF should target those with high NK activity.