Natural killer cells - friend or foe?

The first time I heard the term "natural killer cells" in relation to miscarriages and failed IVF cycles, I thought it sounded awful. As if certain women have these toxic cells in their bodies destroying any potential babies! However, I have since learned that everyone has natural killer cells and they are generally a good thing. They help your body fight off infections and diseases (including cancer) and indicate a strong immune system. The theory, which is quite new in the infertility industry, is that some women (I read somewhere it's around 10-15%) have elevated levels which could then interfere with pregnancies. Initially when an embryo arrives into the womb, it will appear as a something foreign since it will have different DNA, and her body will need to decide that this is something good and should be protected and not fought off. It is a complex process so I guess it's easy to imagine that something might go wrong along the way.

While researching NK cells (which has left me more confused than ever to be honest!) I came across a blog saying that if you have elevated levels then you should figure out why, and not just take medicine to reduce them. That makes sense but I don't think it's so easy. I went to a gastrologist recently to discuss some occasionaly digestive issues I've been having and am now getting tested for celiac, just to rule out any other food intolerances. I hope I don't have any more as living with lactose intolerance is already difficult enough! I'm not sure what else I could be tested for. The gastrologist I went to was actually really uncaring and abrupt. He agreed to do some testing but when I tried to show him the blood tests results, he basically just told me to discuss them with my gyno. I had mentioned my miscarriage following IVF to him to explain why we had done the further blood testing and he looked like he couldn't care less. He certainly didn't show any sympathy. Clearly he doesn't believe that stomach issues may have any connection with infertility. I felt quite upset actually after the encounter. On my way home I was sad thinking about those three IVF potential babies that were transferred into me during the first and second round and what could have been...

These days a lot of people have food allergies and intolerances. It's probably due to the western diet, too many processed foods, plus we eat too much dairy in general. A cow's milk is designed for calves not humans. I still eat dairy with lactase enzyme tablets. Completely cutting it out is just too difficult since I love yoghurts and cheese but I have been trying to reduce the amount. I tried osteopathy two years ago when I was attempting natural fertility options (such as acupuncture) and the lady told me that she has had several women who couldn't get pregnant who she advised to quit dairy for three months and they then fell pregnant shortly after! She had the theory that a lot of people probably have undiagnosed food intolerances that they don't know about but could be causing stomach inflammation. It could be the case that your body then says, oh something is wrong, and the natural killer cells get elevated. One of the women on an IVF forum I frequent was able to substantially reduce her elevated NK cells naturally when she followed the so-called AIP diet (Autoimmune Protocol) which is an even stricter version of the paleo diet. It is great to hear there may be some other ways to treat the NK cells, and I also read something about omega3 helping (I'm taking supplements now), but I don't think I would be able to follow such a restrictive diet for that long!

During my research I came across a website saying how great natural killer cells are, that they fight off cancer and some tips on how to elevate them which seemed ironic since I am trying to do the opposite! In general I rarely get the flu and don't come down with many colds so maybe I do have a strong immune system. The treatment for elevated NK cells can leave you more prone to infections so it's important to be aware of that. I came across IVIG & Intralipid Therapy in IVF: Interpreting Natural Killer Cell Activity for Diagnosis and Treatment which mentions the importance of testing for NK cells in relation to fertility and wishes more reproductive doctors would take it seriously.

However then I also found Fertility Fraud: Natural Killer (NK) Cell Testing which says there are too many false positives and no need for the unnecessary treatments. Another negative article: Natural killer (NK) cells – fertility fraud? which suggests the idea of the human uterus attacking an embroyo it is designed to nurture is "preposterous". And from another post on the same site:
Anxious IVF patients are soft targets for hard marketers. In consulting rooms and online, they’re told their bodies may be sabotaging their pregnancies because their embryos are perceived as infections. This ‘NK’ scare may be completely unfounded. Natural killer cells: you have to hand it to the person who coined that phrase. It’s a mortifying description for vulnerable IVF patients willing to try anything to improve their chances. The truth is, intralipids might help. Might. Not will

The next article I read, Reproductive Immunology – What is the truth about Natural Killer cells? sums it up such;
Studies looking into these cells have produced conflicting results, but the majority of leading scientists in this area dispute that Natural Killer cells are a problem in fertility treatment and pregnancy. Given the potential side effects accompanying Natural Killer cell treatments, there does not seem to be enough justification for undergoing this testing and treatment.

Reading all those of course makes me wonder if the tests and treatments could just be a complete waste of money, unjustified and potentially put my health or that of my future unborn baby at risk. Going through IVF, I am already prepared to take certain risks with my own health but I definitely would not want to negatively affect any children! Then again I also read lots of sites which were on the other side of the controversy, for instance: Miscarriages can be Prevented, and this study which concludes:
The results of present study demonstrated that the level of NK cells as a risk factor is associated with pregnancy loss in women with IVF failure.

There was also this interesting article: Natural Killer Cells & Fertility:Cutting Through the Controversy which summarizes;
Studies are beginning to surface that demonstrate IntraLipid therapy does in fact improve the odds of pregnancy for those with recurrent implantation failure. In fact, well-reputed journals (Human Reproduction (2016) 31 (1): 217–218; “The absence of evidence is not the evidence of absence” and (2015) 30 (7): 1526-1531 “Enough! Stop the arguments and get on with the science of natural killer cell testing”) are publishing articles outlining both the pro’s and con’s of testing natural killer cells. Unfortunately, many people opposed to the testing only cite the publication that argues against it. That being said, not everyone requires testing for natural killer cell activation – it should be reserved for certain patients that have already demonstrated an implantation issue. And treatment of these individuals, should their test be positive, has been successful in thousands of anecdotal cases.

I asked around a bit. Two doctor friends think that having high natural killer cells does not cause fertility issues and the numbers can just be raised due to other factors such as stress and to be wary of any "treatment". I heard from someone else who has a doctor friend in Hannover that specializes in fertility that she has had eight patients helped by the NK treatment, even a few of them who got pregnant naturally after failed IVF! I've also read loads of stories on forums from women who had several miscarriages and then got the treatment which worked for them. It doesn't work for everyone though, I know that. Hearing the positive stories makes me hopeful and I think it could be worth trying in our case. That said, I do feel somewhat uncomfortable about it and will definitely be asking my doctor a lot about the risks and side effects.

Would you pursue the natural killer cell treatment if you were me?