Problem: Changes in endometrial Natural Killer (NK) cells during the luteal phase of the ovarian cycle are important in initiating/maintaining a subsequent pregnancy. In the present study it was investigated whether during the menstrual cycle changes occur also in peripheral blood (PB) NKs.
Method of study: Blood samples during the follicular and the luteal phase were collected from 30 women without fertility problems. Samples were analyzed by flow-cytometry for: (1) NK cells (CD3(-)CD16+CD56+) and (2) intracellular production of interferon-gamma (IFN-gamma) by NK cells. For the comparison and correlation of the two populations between the two phases, Wilcoxon signed-rank test and Spearman's Coefficient were used.
Results: The differences in percentages of CD3(-)CD16+CD56+ cells and that of CD3(-)CD16+CD56+/IFN-gamma+ cells between the follicular and the luteal phase were not statistically significant (10.61 +/- 5.11 versus 9.76 +/- 4.57 and 6.48 +/- 7.90 versus 7.30 +/- 6.77, respectively, P > 0.05). The correlation between the two variables (NK% and NK/IFN-gamma%) was weakly positive (P = 0.07) only in the follicular phase.
Conclusion: The study did not reveal menstrual cycle-depended changes in PB NK cells. Thus, a suggestion to measure these cells in a specific phase of the cycle in order to predict the outcome of a subsequent pregnancy in women with fertility problems is objected.