How do you test for uterine natural killer cells?

We begin first with our immunological laboratory. In the past, we used to perform the testing of NK cells in blood but it is not exactly the same what we have inside the uterus. There is a correlation but not the same so, now, we try to test in blood, in the uterus and sometimes we have discordance and in this case we are doing some clinical intervention – mostly when we have uterine NK cells.

The most prognostic approach is to look at uterine natural killer cells and to do that, they take an endometrial biopsy and then look from that biopsy do different stainings and count the number of uterine natural killer cells versus the normal cells in the uterus and they give out a percentage which will either be low, moderate or high. The theory would be that if you have high natural killer cells, you’re either at a higher risk of miscarriage or you’re at a higher risk of recurrent implantation failure which is you’re putting back multiple good quality blastocyst over several cycles and still not getting pregnant. If you’re diagnosed with uterine high natural killer cells, there are different treatment options depending on what clinic you go to. The most common approach is to give you prognenozole which will reduce the amount of natural killer cells and theoretically improve your chances of implantation and reduce your chances of miscarriage but the evidence is probably weak at best and again should only be done by sort of a center that specializes in that kind of area.

The reported increases in uterine natural killer cells numbers in recurrent implantation failures or recurrent miscarriages has resulted in increasing demand from women with these conditions for measurements of both peripheral blood natural killer cells as well as uterine natural killer cells counts. We need to remember that there is a lack of consensus during this time on the methods used for measuring or reporting uterine natural killer cell numbers. Also there is a lack of a clear definition of what it is considered as normal levels of natural killer cells both in the uterus as well as the peripheral bloods. Last but not least, uncertainty that higher levels of natural killer cells, indeed there are and these numbers cannot be predictive of any adverse pregnancy outcome. Measurements of peripheral blood natural killer cells are considerably easier to make than those of uterine natural killer cells since they do not require any endometrial biopsy to be performed which is an invasive procedure. However the significance of peripheral blood NK cells measurements is still questionable. The available tests include non-invasive blood samples for peripheral blood natural gas cell measurement nevertheless it remains controversial whether peripheral blood measurements reflect conditions at the placental site. A range of measurements can be requested by clinics. Frequently the number and activity of natural killer cells are measured. However, because these tests are looking at NK cells in the blood and not the special NK cells in the uterus, they offer no useful information in relation to pregnancy outcomes. In addition, there are some direct endometrial biopsies that can be obtained. Nevertheless, again, the results still have not been standardized by international literature.