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-γ (IFN-γ) 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.
The differences in percentages of CD3−CD16+CD56+ cells and that of CD3−CD16+CD56+/IFN-γ+ 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-γ%) was weakly positive (P = 0.07) only in the follicular phase.
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.