Changes in endometrial natural killer cell expression of CD94, CD158a and CD158b are associated with infertility.

PROBLEM

Cycle-dependent fluctuations in natural killer (NK) cell populations in endometrium and circulation may differ, contributing to unexplained infertility.

METHOD OF STUDY

NK cell phenotypes were determined by flow cytometry in endometrial biopsies and matched blood samples.

RESULTS

While circulating and endometrial T cell populations remained constant throughout the menstrual cycle in fertile and infertile women, circulating NK cells in infertile women increased during the secretory phase. However, increased expression of CD94, CD158b (secretory phase), and CD158a (proliferative phase) by endometrial NK cells from infertile women was observed. These changes were not reflected in the circulation.

CONCLUSION

In infertile women, changes in circulating NK cell percentages are found exclusively during the secretory phase and not in endometrium; cycle-related changes in NK receptor expression are observed only in infertile endometrium. While having exciting implications for understanding NK cell function in fertility, our data emphasize the difficulty in attaching diagnostic or prognostic significance to NK cell analyses in individual patients.