Archives of Medicine and Health Sciences

ORIGINAL ARTICLE
Year
: 2019  |  Volume : 7  |  Issue : 2  |  Page : 191--194

Peripheral blood level of natural killer cells in pregnant women with recurrent spontaneous abortion during the 6–12 weeks gestation


Sung-Guk Kim, Mi-Yong Paek, Il Gyong Ko 
 Department of Obstetrics and Gynecology, Pyongyang Medical College, Kim Il Sung University, Pyongyang, Democratic People's Republic of Korea

Correspondence Address:
Dr. Sung-Guk Kim
Department of Obstetrics and Gynecology, Pyongyang Medical College, Kim Il Sung University, Pyongyang
Democratic People's Republic of Korea

Abstract

Background and Aim: The study was performed to confirm the clinical characteristics and peripheral blood level of natural killer (NK) cells as a diagnostic index in women with recurrent spontaneous abortion (RSA) comparing with normal pregnant women. Materials and Methods: Consultation with all patients was conducted to obtain the number and timing of previous miscarriages and signs and symptoms of abortion progress. Assessment of peripheral blood NK cell level was performed by flowcytometric analyses. Results: Women with RSA have brown-colored vaginal bleeding and history of more than three consecutive miscarriage, while the percentage of peripheral blood NK cell within blood lymphocytes was more than 18.1%. Conclusion: In the current study, RSA patients (6–12 weeks') showed significantly higher level of peripheral blood NK cells (>18.1%) compared to that of normal gravidas. Further studies are required to clarify the precise mechanism how NK cells affect the progression of healthy pregnancy and investigate clinical evidence whether therapies to lower the level of NK cells can decrease the rate of RSA.



How to cite this article:
Kim SG, Paek MY, Ko IG. Peripheral blood level of natural killer cells in pregnant women with recurrent spontaneous abortion during the 6–12 weeks gestation.Arch Med Health Sci 2019;7:191-194


How to cite this URL:
Kim SG, Paek MY, Ko IG. Peripheral blood level of natural killer cells in pregnant women with recurrent spontaneous abortion during the 6–12 weeks gestation. Arch Med Health Sci [serial online] 2019 [cited 2020 Jun 4 ];7:191-194
Available from: http://www.amhsjournal.org/text.asp?2019/7/2/191/273069


Full Text



 Introduction



Recurrent spontaneous abortion (RSA) is defined by the occurrence of two or more consecutive failed pregnancies.[1],[2],[3] Spontaneous abortions are mostly caused by chromosomal abnormalities in embryos, and anatomic uterine defects appear to predispose women to reproductive difficulties.[4],[5],[6],[7],[8],[9],[10],[11] Mechanisms of unexplained reproductive failure (infertility and RSA) involve immune-mediated pathways, including the presence of a predominant T-helper (Th) 1-Type immunity during pregnancy, a decrease in T-regulatory cells and an increase in natural killer (NK) cells.[12],[13],[14] These phenomena can occur locally, at the site of implant, and can be observed also in the peripheral blood.[5],[15],[16] It has been shown that the interaction between human leukocyte antigen (HLA) molecules and NK cells is the checkpoint of the regulation of the NK cell activity at the maternal–fetal interface. NK cells are innate immune effectors that are able to exert a cytolytic activity against infected and tumor cells and to produce immunomodulatory cytokines without HLA restriction or prior sensitization. Peripheral blood NK cells comprise about 10%–12% of blood lymphocytes and are strikingly suppressed in normal early pregnancy.

On the other hand, NK cells constitute the predominant leukocyte population present in the endometrium at the time of implantation and in early pregnancy. Decidual NK cells (dNK) are a specific CD16-cell subset that includes selective expression of CD9, galectin-1, and glycodelin, with regulatory effects on T-cells.[17],[18] Since peripheral NK cells downregulate dNK under the influence of estrogen and progesterone levels, both the hormonal status and the NK cytokines contribute to the shift toward a Th2 response that characterizes normal pregnancy.

In 1981, Taylor first described about human immunotherapy with white blood cells and Beer reported the efficacy of immunotherapy with husband white blood cells in treatment for RSA women.[4],[15],[19],[20],[21],[22] As the incidence of clinically evident abortion is approximately 15%, the probability of three times of consecutive pregnancy losses could be estimated as 0.34%.[6],[23] However, the incidence of recurrent abortion is 1%–5% of all pregnancy. Moreover, the probability of abortion after three times of previous abortion is 26.2%–60.0%.[1],[2],[6],[17],[23],[24],[25] The study was performed to confirm characters of the medical symptoms and the percentage of peripheral blood NK cell within blood lymphocytes with the RSA during the pregnancy 6–12 weeks. When these factors are high, it is of high possibility of the RSA.

 Materials and Methods



One hundred and twelve pregnant women with RSA who were admitted to the Pyongyang Maternity Hospital since January 2009–July 2011 were involved in study group, and thirty normal pregnant women with no history of RSA and no sign of imminent abortion in pregnancy of 6–12 weeks were involved in control group. Three cases with luteal insufficiency, 2 cases with uterine fibroids, 1 case with positive Rh, 1 case with uterine anomaly, 3 cases with antiphospholipid syndrome, and 1 case with thyroid disorder were excluded. All the patients with RSA were confirmed to have fetal heartbeat by ultrasound examination.

As shown in [Table 1], 70 cases (62.5%) were 25–29 years, accounted for the majority of all patients.{Table 1}

Consultation with all patients were conducted to obtain the number and timing of previous miscarriages, subjective symptoms, and objective signs of abortion progressAssessment of peripheral NK cell level was performed by flowcytometric analyses.

One milliliter of peripheral blood was sampled in sterile test tube preprocessed with ethylenediaminetetraacetic acid K2 so that it would not be clottedFifty microliters of the blood were added to the Falcon test tube with cap which was previously added with 10 μl of CD56-labeled fluorescence antibody solution, and then incubated in dark room for 15 minThen, 1 ml of FACS Lysing solution was added to the tube, which was then incubated in dark room for 10 min and then centrifuged at 1500 rpm for 5 minSupernatant was disposed, and then 500 μl of suspension was agitated to make cell suspension, which was then assessed to evaluate the ratio of NK cells in total lymph cells.

Statistical analysis was performed by Student t-test for numerical values and Chi-square test for proportional values.

 Results



1. Pregnant women with RSA has history of regular bleeding, little morning sickness, lower back or lower abdomen pain, and vaginal bleeding of brown color [Table 2], [Table 3], [Table 4], [Table 5].{Table 2}{Table 3}{Table 4}{Table 5}

Regularity of miscarriage timing

As shown in [Table 2], 96 cases (85.7%) had regular miscarriages, which accounted for the majority of all patients.

Presence of morning sickness

[Table 3] showed that 20 cases (17.9%) had morning sickness and 92 cases (82.1%) had no sickness, and majority of patients had no morning sickness.

Subjective symptoms of miscarriage

As shown in [Table 4], 4 patients (3.6%) with RSA had lower back pain, 11 patients (9.8%) lower abdominal pain and black red bleeding, and 81 patients (72.3%) brown bleeding with no pain, which was the most frequent symptom.

2. Levels of peripheral blood NK cells with the RSA during the pregnancy 6–12 weeks.

As shown in [Table 5], peripheral blood NK cell level was 23.8% ± 5.5% in pregnant women with RSA, which was significantly higher than those (8.9% ± 2.8%) in normal pregnant women (P< 0.01). Moreover, the NK cell levels in all normal pregnant women were lower than 18%, while 105 patients (93.7%) had NK cells higher than 18%.

 Discussion



We analyzed NK cell levels in all the women enrolled.[8],[17],[18],[26],[27],[28],[29],[30],[31] We found that the RSA women had significantly higher NK cell levels than controls. These results are in accordance with other studies comparing the percentage of peripheral blood NK cells in RSA women versus controls.[9],[18],[28],[32],[33],[34]

It is possible that elevated NK cell levels represent an evidence of such broadly based immune system activation, and they may characterize women with RSA according to alloimmune mechanisms of the pregnancy failure.[35],[36],[37] The result of our research suggested that the assessment of the percentage of peripheral blood NK cell may play as diagnostic tool in women with RSA. We described that NK cell percentage may be a useful test to differentiate women with RSA and fertile controls.

The cutoff value of NK cell percentage obtained in our study population resulted in accordance with data in the literature. According to the threshold value for abnormal NK cell levels, we observed that the prevalence of women with abnormal NK levels was, as expected, higher among the RSA women with the respect to the comparison group.

As the incidence of clinically-evident abortion is approximately 15%, the probability of three times of consecutive pregnancy losses could be estimated as 0.34%.[6],[23] However, the incidence of recurrent abortion is 26.2%–60.0%.[24],[25] We determined clinical and NK cell level features in patients with RSA. This result suggests that these parameters could be used to estimate high risk of miscarriage.

More studies are needed to confirm the role of NK cell assessments as a prognostic test for women with reproductive failure.

 Conclusion



In this study, we have assessed the levels peripheral NK cells in early-trimester recurrent abortion patients (6–12 weeks' gestation) in our country and compared with that of literature. In the current study, RSA patients (6–12 weeks') showed significantly higher peripheral blood NK cells (>18.1%) compared to that of normal gravidas. Although this study has confirmed the relationship between elevated levels of peripheral NK cells and the incidence of RSA, further studies are required to clarify the precise mechanism how NK cells affect the progression of normal pregnancy. Furthermore, clinical evidence whether therapies to lower the level of NK cells can decrease the rate of RSA should also be investigated.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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