The Compatibility Gene by Daniel M Davis: "I am very rare but my wife is rather common"

The scientist Daniel M Davis has told the story of genetic compatibility - and the rejection that is its opposite - with great insight and decades of research. It's a field that may yield significant treasures in the decades to come.

The Compatibility Gene
Daniel M Davis
Allen Lane, 256pp, £20

“I am very rare but my wife is rather common.” This is not a sentence that would normally endear an author to you, let alone make you feel a little sorry for him. The thing is, it’s not great being exotic. Should Daniel M Davis get seriously ill, his chances of finding a transplant match are very bad. When he tells you that his wife is not one in a million but one in 100,000, you should feel good for her. Davis is one in four million, according to the genetic tests that the couple underwent. That’s very bad news, transplant-wise.

This all comes down to what Davis terms the “compatibility genes”. They are the set of genes that determine the make-up of your immune system and make you who you are.

We worry about where we came from. There is not a human civilisation on the planet that does not pay attention to its ancestors in some way. TV genealogy shows have probably amplified this trait, encouraging us to treasure our roots (or despair at them) in ever larger measure. So it’s no wonder we don’t cope well with the idea of organ transplantation: it messes with everything.

A study carried out in Sweden demonstrates the problem. In interviews with patients who had received someone else’s kidney, almost all of the subjects said that they felt it was best not to know too much about the donor. For some irrational, inexplicable reason, we are psychologically sideswiped by the idea that someone else’s meat has been installed inside our own. Some patients even worried about worrying about it, expressing a fear that too much “brooding” over the donor could lead their bodies to reject the foreign tissue.

We now know, thanks to a half-century of scientific sleuthing, that this isn’t true. Rejection of foreign bodies results from the activities of the compatibility genes. Davis’s enlightening book tells the extraordinary story of that discovery. As well as dealing with foreign tissue, the compatibility genes seem to influence our selection of biologically beneficial partners. It turns out that we look for complementary immune systems that enhance the chance of our offspring’s survival. Get it wrong at your peril: the compatibility genes are, it seems, frequently to blame in miscarriages. The contributions frommother and father have to be a good complementary pairing for a pregnancy to be successful. If Davis’s wife had chosen a more “common” man, she might have found herself with someone whose genes were too similar to her own, with adverse effects on the couple’s fertility. As Davis puts it, “Differences in our immune-system genes can influence who gets born.”

Sadly, science has not yet given us ways to cope with these differences. The best you can do is try to find a partner who somehow smells right. Evolution’s finest innovation might be the nose: we use it to check whether someone else’s immune system is complementary to our own.

Evolution is not perfect, however: given that as many as one in three pregnancies ends in miscarriage, cleary the smell is too subtle. Either that or we are all washing too thoroughly (or not doing enough investigative snogging).

It is almost ironic that the scientists who laid the foundations of this kind of research also had coupling issues. The Nobel laureate biologist Peter Medawar’s work elucidating what causes the rejection of transplants was so intense that he told his wife that she had claim on his love but not his time (and that he would be fine with an open marriage). The Danish biologist and sadomasochism fan Niels Jerne had a string of affairs before his wife (who had her share of lovers) committed suicide; it was only later, suppressing his grief with a gruelling work schedule, that Jerne uncovered the protective powers of antibodies. The Austrian Karl Landsteiner discovered the vital distinctions we know as blood groups. He also lived with his mother until she died. When he married shortly after that, the new Mrs Landsteiner faced the nightly distraction of her mother-in-law’s death mask on the bedroom wall. To her credit, the couple did manage to have a child.

Many more scientists are threaded through the pages of Davis’s thoughtful book and they all share one thing: the grinding heartbreak that is the slow progress of scientific discovery. It’s a heartbreak that Davis knows well; he is a leading figure in this subject. Though the science behind what causes our body to recognise itself and reject foreign material is more than 60 years old, he tells us, the conclusions we can draw from it are still fairly limited. Nonetheless, The Compatibility Gene is a fascinating, expertly told story of a field that may yield significant treasures in the decades to come.

Michael Brooks is the New Statesman’s science columnist 

The science behind our bodies' rejection of foreign material is 60 years old, Davis writes, but the conclusions we can draw are still limited. Photograph: Getty Images.

Michael Brooks holds a PhD in quantum physics. He writes a weekly science column for the New Statesman, and his most recent book is At the Edge of Uncertainty: 11 Discoveries Taking Science by Surprise.

This article first appeared in the 02 September 2013 issue of the New Statesman, Syria: The west humiliated

Davide Restivo at Wikimedia Commons
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Scientists have finally said it: alcohol causes cancer

Enough of "linked" and "attributable": a new paper concludes that alcohol directly causes seven types of cancer.

I don't blame you if you switch off completely at the words "causes cancer". If you pay attention to certain publications, everything from sunbeds, to fish, to not getting enough sun, can all cause cancer. But this time, it's worth listening.

The journal Addiction has published a paper that makes a simple, yet startling, claim: 

"Evidence can support the judgement that alcohol causes cancer of the oropharynx [part of the throat], larynx, oesophagus, liver, colon, rectum and [female] breast"

So what's especially significant about this? 

First, scientists, unlike journalists, are very wary of the word "causes". It's hard to ever prove that one action directly led to another, rather than that both happened to occur within the same scenario. And yet Jennie Connor, author of the paper and professor in the Preventive and Social Medicine department at the University of Otago, New Zealand, has taken the leap.

Second, alcohol not only causes cancer of one kind – the evidence supports the claim that it causes cancer at seven different sites in our bodies. There was weaker evidence that it may also cause skin, prostate and pancreatic cancer, while the link between mouth cancers and alcohol consumption was the strongest. 

What did we know about alcohol and cancer before?

Many, many studies have "linked" cancer to alcohol, or argued that some cases may be "attributable" to alcohol consumption. 

This paper loooks back over a decade's worth of research into alcohol and cancer, and Connor concludes that all this evidence, taken together, proves that alcohol "increases the incidence of [cancer] in the population".

However, as Connor notes in her paper, "alcohol’s causal role is perceived to be more complex than tobacco's", partly because we still don't know exactly how alcohol causes cancer at these sites. Yet she argues that the evidence alone is enough to prove the cause, even if we don't know exactly how the "biologial mechanisms" work. 

Does this mean that drinking = cancer, then?

No. A causal link doesn't mean one thing always leads to the other. Also, cancer in these seven sites was shown to have what's called a "dose-response" relationship, which means the more you drink, the more you increase your chances of cancer.

On the bright side, scientists have also found that if you stop drinking altogether, you can reduce your chances back down again.

Are moderate drinkers off the hook?

Nope. Rather devastatingly, Connor notes that moderate drinkers bear a "considerable" portion of the cancer risk, and that targeting only heavy drinkers with alcohol risk reduction campaigns would have "limited" impact. 

What does this mean for public health? 

This is the tricky bit. In the paper, Connor points out that, given what we know about lung cancer and tobacco, the general advice is simply not to smoke. Now, a strong link proven over years of research may suggest the same about drinking, an activity society views as a bit risky but generally harmless.

Yet in 2012, it's estimated that alcohol-attributable cancers killed half a million people, which made up 5.8 per cent of cancer deaths worldwide. As we better understand the links between the two, it's possible that this proportion may turn out to be a lot higher. 

As she was doing the research, Connor commented:

"We've grown up with thinking cancer is very mysterious, we don't know what causes it and it's frightening, so to think that something as ordinary as drinking is associated with cancer I think is quite difficult."

What do we do now?

Drink less. The one semi-silver lining in the study is that the quantity of alcohol you consume has a real bearing on your risk of developing these cancers. 

On a wider scale, it looks like we need to recalibrate society's perspective on drinking. Drug campaigners have long pointed out that alcohol, while legal, is one of the most toxic and harmful drugs available  an argument that this study will bolster.

In January, England's chief medical officer Sally Davies introduced some of the strictest guidelines on alcohol consumption in the world, and later shocked a parliamentary hearing by saying that drinking could cause breast cancer.

"I would like people to take their choice knowing the issues," she told the hearing, "And do as I do when I reach for my glass of wine and think... do I want to raise my risk of breast cancer?"

Now, it's beginning to look like she was ahead of the curve. 

Barbara Speed is a technology and digital culture writer at the New Statesman and a staff writer at CityMetric.