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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.

Transplant lab.
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.

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