Cyclic Changes and Relationship between Peripheral and Endometrial NK Cells from Women with Repeated Failure after Artificial Insemination by Donor Sperm

Problem Cyclic changes of peripheral natural killer (p NK ) cells and/or endometrial NK (e NK ) cells during menstrual cycle remain controversial, and their relationship remains uncertain. Method of study Peripheral blood and endometrial biopsies were simultaneously obtained from women ( n  = 23) undergoing artificial insemination with donor sperm ( AID ) for at least three cycles at both proliferative (days 9–11) and secretory phases (days 20–23) of menstrual cycle. The percentages of CD3 −  CD56 + , CD3 −  CD56 dim  CD16 + , CD3 −  CD56 bright  CD16 − p NK , and e NK cell subsets within lymphocytes were determined by three‐color flow cytometry. The correlation between the percentages of p NK and e NK cells was further analyzed by S pearman's test. Results The percentages of CD3 −  CD56 + , CD3 −  CD56 dim  CD16 + , and CD3 −  CD56 bright  CD16 − p NK cells were not statistically different between the proliferative and secretory phases ( P  > 0.05, respectively). However, the percentages of CD3 −  CD56 + and CD3 −  CD56 bright  CD16 − eNK cells were significantly decreased at the secretory phase, compared with those in the proliferative phase ( P  < 0.05, respectively). No correlation between the percentages of all pNK cell parameters and those of CD3 −  CD56 bright  CD16 − eNK cells (the major subset of NK cells in uterus) was found in the same women throughout the menstrual cycle ( P  > 0.05). Conclusion We found a menstrual‐cycle‐dependent change in the percentage of e NK cells in women undergoing AID treatment, but not p NK cells. Moreover, the percentage of p NK cells may not reflect that of e NK cells during menstrual cycle.