Am J Reprod Immunol. 2017 Nov;78(5). doi: 10.1111/aji.12708

Abnormal ratio of CD57+ cells to CD56+ cells in women with recurrent implantation failure 

Ruiwei Jiang, Guijun Yan, Jun Xing, Zhilong Wang, Jianjun Zhou, Lijun Ding, Haixiang Sun

From Center for Reproductive Medicine, Department of Obstetrics and Gynecology, the Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing 210008, China

Correspondence should be addressed to Haixiang Sun, Center for Reproductive Medicine, Department of Obstetrics and Gynecology, the Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing 210008, China, Email: stevensunz@163.com

 

Abstract

Here we define a more precise parameter for a better understanding of natural killer (NK) cells and its relation with regulatory T cells (Tregs) in women with recurrent implantation failure (RIF). We measured the percentages of CD56+ cells, CD57+ cells, and Foxp3+ cells in the endometrium and blood from 23 normal controls and 32 women with RIF were by immunocytochemistry and flow cytometry. In the mid-secretory endometrial, the percentage of CD57+ cells was significantly higher in the women with RIF [1.24% (0.32-4.68%)] than that in normal controls [0.92% (0.17-2.3%)] (p < 0.05), while Foxp3+ cells in women with RIF were significantly decreased [0.13% (0.02-0.27%) vs 0.19% (0.04-0.27%)] (p<0.01). Women with RIF had significantly increased ratio of CD57+ cells to CD56+ cells in both the endometrium (p < 0.01) and blood (p < 0.05), and decreased percentage of Foxp3+ cells in the blood (p < 0.05). There was a significant negative correlation between the ratio of CD57+ cells to CD56+ cells and the percentage of Foxp3+ cells in the blood (p < 0.05). In conclusion, women with RIF has higher NK cells cytolytic activity, which is negatively correlated to the level of Tregs.

https://doi.org/10.1111/aji.12708

 

Supplement:

Successful implantation of a blastocyst into the endometrium is essential for reproduction. It is a complex process that requires synchronization of maturational events in the developing embryo, maternal hormonal changes and immune responses. For women who experience RIF with good-quality embryos, the endometrial microenvironment may be the key factor. The endometrium supports further implantation mediated by immune cells, cytokines, growth factors, chemokines, and adhesion molecules at implantation window. During this period, 65-70% of the immune cells in the endometrium are uterine natural killer (uNK) cells that belong to the innate immune compartment. Macrophages and dendritic cells are also detected, together with adaptive immune T cells, such as regulatory Tregs.1 A synergism of these factors is critical for successful implantation and subsequent conception.

 

After ovulation, uNK cells proliferate vigorously so that by the late secretory phase they account for at least 30% of the endometrial stroma. The number of CD56+ cells remains high during early pregnancy and comprises 70% of the lymphocytes at the interface between maternal decidua and the invading trophoblast. It is generally believed that uNK cells are likely to play a critical role in trophoblast invasiveness, migration and placentation. Maternal CD56+ cells in the endometrium of some women with RIF are significantly different from those with known fertility, while the conclusion remains controversial.2 CD57 is generally regarded as a marker of terminal differentiation in human CD8+ T cells, but a recent study has found that CD57 defines a subtype of more mature NK cells. CD57+ NK cells have been detected in both the endometrium and peripheral blood, but no obvious trend was observed in either absolute numbers or percentage counts throughout the menstrual cycle.3 Although uNK cells in endometrium are thought with lower cytolytic activity and increased cytokine production, an increased CD57+ NK cells number has been found in the decidua of spontaneous abortions, and these cells can become activated by local cytokines to attack the trophoblast.4

 

 

Fig. 1. Endometrial NK cells and Tregs in women with RIF and normal controls.

Photomicrograph of immunostaining in mid-secretory endometrium for CD45 from (a) a normal woman and (b) a woman with RIF, CD56 from (d) a normal woman and (e) a woman with RIF, CD57 from (g) a normal woman and (h) a woman with RIF, and Foxp3 from (g) a normal woman and (h) a woman with RIF. Percentages of stromal cells positive for (c) CD45, (f) CD56, (i) CD57, and (l) Foxp3 in mid-secretory endometrium from normal controls (n=23) and women with RIF (n=32). Bar = 200 μm. RIF, recurrent implantation failure; *, P<0.05; **, P<0.01.

 

Tregs play a key role in protection of embryos when maternal immune cells first contact fetal antigens associated with invading trophoblasts. In mice, Tregs depletion leads to gestation failure. Some studies have found a decreased Foxp3 mRNA level in Tregs in primary unexplained infertility and infertile women with endometriosis.5 One of our previous studies has indicated that an elevated level of circulating Tregs is associated with increased rates of pregnancy and live births after IVF-ET treatment.6 In addition, Tregs are thought to suppress the NK cell-mediated immune response during embryo implantation and pregnancy.

 

Here, we speculated that the measurement of ratio of CD57+ cells to CD56+ NK cell is a more precise approach to evaluate the immune status regarding embryo implantation, which is related with the level of Tregs. So we examined the distributions of endometrial and peripheral CD56+ cells, CD57+ cells, and Foxp3+ cells in women with RIF (Figure 1 and 2). Women with RIF had significantly increased ratio of CD57+ cells to CD56+ cells in both the endometrium and blood, and decreased percentage of Foxp3+ cells in the blood. In addition, we analyzed the relation between NK cells and Tregs in women with RIF and found a significant negative correlation between the ratio of CD57+ cells to CD56+ cells and the percentage of Foxp3+ cells in the blood (Figure 3).

 

 

Fig. 2. Peripheral blood NK cells and Tregs in women with RIF and normal controls.

Peripheral blood was stained for NK cells and Tregs. The analysis gate is set for (a) CD4+ cells (P1). (b) The percentage of CD25+Foxp3+ cells (Q2-1) in P1 is calculated. The analysis gate is set for (d) CD45+ cells (P2), (e) CD56bright cells (P3) by excluding the negative control. (g) The percentage of CD57+ cells in P3 is calculated. Percentages of (c) CD25+Foxp3+ cells in CD4+ cells, (f) CD56bright cells in CD45+ cells and (h) CD56brightCD57+ cells in CD45+ cells from normal controls (n=19) and women with RIF (n= 23). RIF, recurrent implantation failure; *, P<0.05; NS, not significant.

 

 

Fig. 3. The ratio of CD57+ cells to CD56+ cells in both the endometrium and peripheral blood.

(a–b) The ratio of CD57+ cells to CD56+ cells in the (a) endometrium and (b) peripheral blood from normal controls and women with RIF. (c-d) Correlation between the ratio of CD57+ cells to CD56+ cells and the percentage of Foxp3+ cells in the (c) endometrium and (d) peripheral blood of women with RIF. RIF, recurrent implantation failure; *, P<0.05; **, P<0.01.

 

 

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