Sexual intercourse with pyospermia decreases uterine CD16-/CD56 bright natural killer cells in women with infertility

PROBLEM: In the uterine endometrium and the first trimester decidua, there are a number of immune cells derived from the bonemarrow that are capable of responding to alloimmune stimulations from the embryo. Themain population of endometrial NK cell is cytokine producing CD16-/CD56bright NK cells, whereas the most abundant population in peripheral blood NK cells is cytotoxic CD16+/CD56dim NK cells. We previously reported that the increase in cytotoxic NK cells in peripheral blood and the endometrium have a beneficial effect on the therapeutic results of in vitro fertilization andembryo transfer (IVF-ET). Wehave also reported that seminal plasmaplays an important role in the recruitment of CD56bright NK cells into the endometrium. The present study was aimed to investigate the influence of sexual intercourse onNK cell subsets in the mid-secretory endometrium using flow cytometry. METHODS: This study was designed as a prospective study. All study subjects had signed informed consents prior to entry to this study, in accordance with local IRB protocol. All subjects who were planning to have invitro fertilization and embryo transfer (IVF-ET) had sexual intercourse before the endometrial sampling without any contraceptive devices. The mid-secretary endometrium was obtained from 234 women, and then submitted for flow cytometric analysis. Endomerial NK cell subpopulation was analyzed for the expression of CD16 and CD56 using 3-color flow cytometry. Semen analysis was performed at the time of oocytes pick up and was classified according to the World Health Organization (WHO) 2010 guideline. Of 234 semen samples, 10 were diagnosed as pyospermia (pyospermia group), and 224 as not-pyospermia (non-pyospermia group). RESULTS: There were no differences between 2 groups in the total sperm concentration and the motile sperm concentration, or in the percentage of CD56+ NK cells. The percentage of CD16-/CD56+ cells, however, was lower in pyospermia group (25.9±21.7%) compared with that in non-pyospermia group (35.4±18.2%). The percentage of CD16-/CD56bright cells was significantly lower in pyospermia group (28.0±27.8%) compared with that in not-pyospermia group (42.9±22.1%, p< 0.01). CONCLUSIONS: Our study firstly demonstrated that pyospermia has a harmful influence on endometrial NK cell subsets. The immunologically advantageous condition for successful pregnancies after sexual intercourse may give support to the hypothesis that seminal fluid may act as a regulator of endometrial immune cells and an inducer of feto-maternal immune tolerance. Further research should be undertaken to reveal the biological actions of seminal munology 94 (2012) 5–130