Natural killer (NK) cells – fertility fraud?

18 Nov Natural killer (NK) cells – fertility fraud?

Are natural killer (NK) cells really a threat to fertility and pregnancy? Clinics selling so-called reproductive immunology treatments say yes – or at least maybe. Others say no and ask for the research to back it up. Here’s the truth about natural killer cells. It may surprise you.

First, the case against. And it’s a strong one. Dr. Norman Shreeve, a highly regarded expert in obstetrics and gynaecology at the University of Cambridge, recently said: ‘There is no evidence to suggest that any currently available measurement of NK cells… can reliably guide treatment of fertility’. This is echoed by Professor Lesley Regan, another eminent figure in the fertility world, who can find no medical basis ‘to justify the use of these tests and treatments’.

Strong stuff. And a clear indictment of an industry aggressively offering fertility patients expensive ‘treatments’ and ‘therapies’ for natural killer cells. It’s well known that NK cells form part of the blood’s immune response to bacteria, viruses and cancers. But it’s highly questionable whether NK cells in the uterus – which do exist – attack in the same way as blood NK cells. More fundamentally it begs the obvious question: why on earth would a human uterus attack the embryo it is designed to nurture? The proposition seems preposterous.

As we’ve said before in this blog, natural killer cell therapy is an easy sell to anxious couples battling infertility. Just look at the prices being charged at UK clinics for the suppression, or down regulation, of uterine NK cells. We found one clinic charging £450 for a single intralipid infusion to ‘stabilise your immune system’. Destabilise your bank balance, more like – you need at least three infusions per treatment cycle. Or the private consultant charging £2,000 for intravenous immunoglobulin (IVIG) therapy. £2,400 for an NK uterine biopsy? £1,400 for a NK blood test? Welcome to the world of reproductive immunology – an entirely unregulated wing of the UK’s private fertility industry.

As Dr. Shreeve also points out, there’s no globally accepted reference range for uterine NK cell testing, making interpretation and comparison of results inconsistent. Blood NK testing for fertility is seemingly meaningless because there’s no clear link between blood NK cells and uterine NK cells. And suppressing the body’s immune system during pregnancy may have harmful side effects.

It’s only fair to mention the research in favour of natural killer cell treatment for fertility. There’s the small study from 2010 that suggested intralipids help patients who’ve had previous miscarriages (read our view on this). And the small study from Australia that found certain benefits in using the steroid Prednisone (read our view on that). And the small study from 2012, slightly supportive, into the use of immunoglobulin therapy on IVF patients with previous failures. And something a bit more promising from the University of Warwick in 2017.

It doesn’t amount to much, though the Warwick study has more meat on the bones. Other studies are less generous. No large-scale, randomized trials into NK treatment for infertility exist. The HFEA discredits it. But for the natural killer cell industry, glossily marketed and ready to take cash from fertility patients willing to try anything to boost their chances, it’s enough. And it’s only fair to suggest that, occasionally, immunological intervention might make a difference. Might. That hope is all the industry needs. Fertility treatment is, after all, a market in hope.

Some might argue that NK cell treatment providers should examine their consciences. Or at least the way they market and explain their services. Since that probably won’t happen, tighter regulation of largely unproven fertility treatments is needed. In the UK, the number of clinics and one-man bands charging absurd sums of money for NK treatments is troubling. All they have to do is provide a service with reasonable care and skill. That’s not the same as providing a service you actually need.