What are Natural Killer (NK) cells?
NK cells are a type of lymphocyte - an immune cell - normally circulating in blood. They make up a large part of the immune system. NK cells play a major role in the rejection of tumors and cells infected by viruses. They kill those cells by apoptosis (cell shrinkage). There is evidence to suggest that an imbalance of activity of NK cells in the blood of some women could be contributing to miscarriage (Ntrivalas et al., 2005). More recently, an imbalance in the presence of NK cells was also found in the blood of women whose embryos failed to implant in the womb. (Baltadzheiva et al., 2010).
Some clinics offer blood tests to measure the level of NK cells in your blood as well as tests that measure their effectiveness. These blood tests will only measure NK cells in the blood and cannot measure or test NK cells in the uterus. Although the evidence regarding a link between blood and uterine NK cells is limited, it was recently shown that NK cells in the blood could reflect changes in uterine NK cell levels (Park et al., 2010).
What do uterine NK cells do?
The same NK cells are also found in the lining of the womb. Uterine NK (uNK) cells are present in large numbers in the wall of the womb at implantation and in the early months of pregnancy. They seem to help the placenta link up with your blood vessels and so set up a healthy supply line to the fetus. However, scientists do not know exactly how they do it. (In mice that lack NK cells in the womb, development of the placenta is abnormal and the young are smaller than usual). Uterine NK cells appear to be essential and very important regulators of successful implantation and pregnancy (Acar et al., 2010; Schmitt et al., 2008). There is no evidence that uterine NK cells are destructive and attack placental or embryonic cells.
What tests are offered?
We have developed an accurate method of testing the number and the activity of blood and uterine NK cells in our laboratories as a part of our ongoing research programme. It is important to note that these tests, and any treatment based on them, are in their early days and there is limited scientific evidence to show they are effective.
Currently we are the only clinic in the UK that is able to offer the uterine NK cell count test.
How are the tests done?
How long do the results take?
The results should be available within 4 weeks. They are sent to you with a letter that explains the findings.
What do I do if I want to have the test(s)?
You will need to contact Sue Hilton on 0151 702 4261
An information leaflet will be sent to you
An appointment can be made for you to see the consultant
What will happen at my appointment?
What happens if/when I have uterine sampling?
A urine pregnancy test will be carried out.
You will have a transvaginal ultrasound scan (with empty bladder).
An endometrial sample will be taken.
You should allow at least 90 minutes for your appointment
What are the possible risks from uterine sampling?
The risk of any damage to your womb during the procedure is very small. If any damage should occur, it should heal without further treatment. If the sample is taken whilst you are pregnant, it could possibly cause a miscarriage, but we will do a pregnancy test for you before you have a uterine sample taken.
Are there any side effects from the uterine sampling?
You may experience some mild discomfort whilst the sample is being taken.
What are the benefits of the tests?
The results of the test may indicate that treatment could help you.
What treatments are offered?
Treatments that may be beneficial include: high-dose steroids intravenous immunoglobulin (IVIg) tumour necrosis factor-a (TNF) blocking agents intralipids These treatments are not licensed for use in reproductive medicine. As with all medical interventions they carry risks and potential side effects. If you wish to consider having these treatments you will be given further information and asked to sign a consent form.
Please see our ‘Immunological treatments’ leaflet and the HFEA website for further information (http://www.hfea.gov.uk/fertility-treatment-options-reproductive-immunology.html)
Acar N, Ustunel I, Demir R. (2010) Uterine natural killer (uNK) cells and their missions during pregnancy: A review. Acta Histochem. Jan 2.
Baltadzheiva D, Penkova K, Stamenov G, Dimitrova D, Michailova A. (2010) Expression of activating and inhibitory receptors on peripheral blood natural killer cell subsets of women with reproductive failures. Akush Ginekol.; 49(4): 12-17.
Ntrivalas EI, Bowser CR, Kwak-Kim J, Beaman KD, Gilman-Sachs A. (2005) Expression of killer immunoglobulin-like receptors on peripheral blood NK cell subsets of women with recurrent spontaneous abortions or implantation failures. Am J Reprod Immunol.; 53(5): 215-221.
Park DW, Lee HJ, Park CW, Hong SR, Kwak-Kim J, Yang KM (2010) Peripheral blood NK cells reflect changes in decidual NK cells in women with recurrent miscarriages. Am J Reprod Immunol; 63: 173–180
Schmitt C, Ghazi B, Bensussan A. (2008) NK cells and surveillance in humans. Reprod Biomed Online; 16(2): 192-201.