“The fact that these genes are right next door to your HLA genes suggest they may have some role in mate selection,” he said.
Two weeks after posting our samples, following a car journey that did little to enhance our compatibility, my wife and I finally locate the histocompatibility laboratories. As we are ushered into a boardroom, I prepare myself for revelations I may not like, or even comprehend.
The labs do not analyze HLA types to facilitate dating. They do rather more important work, matching tissue types for bone marrow transplants and saving lives. Sharing HLA types with a donor reduces the risk that a stem cell graft will be seen as “non-self,” and rejected.
There are 500,000 potential donors on Anthony Nolan’s register, and they have access to a further 750,000 from other UK registers, plus a worldwide database with 22 million names on it. They also spend a lot of time educating the public about stem-cell donation, which is not the invasive surgical procedure it once was.
“It’s actually very straightforward,” said Ellen Marshall, Anthony Nolan’s communications manager. “Ninety percent of people donate by a method called peripheral blood stem cell collection, which is similar in nature to giving blood.”
Basically, they take blood out of one arm, harvest stem cells from it, and return it to the other arm. You only donate in the event that you are matched with a recipient, and to join the register all you have to do is send them your spit, as I did.
I can not make much sense of the test results without first getting a bit of education from Marsh. We are primarily concerned, he said, with the five major histocompatibility genes: HLA-A, HLA-B, HLA-C, HLA-DR and HLA-DQ. You inherit these in a block and you end up with two sets, one from each parent. Each set is known as a haplotype; each specific version of a gene is called an allele. Without further testing it is not possible to know for sure which alleles came from which parent, but because certain ones are commonly found together, they can make a statistical best guess about your haplotypes.
“We’ll do you first,” Marsh says, handing me a sheet of paper with some numbers on it. “That’s your tissue type.”
I nod, because it seems like the right thing to do. My HLA-A allele on one haplotype, he says, goes by the name HLA-A32:01:01. Lots of people have it, apparently. The HLA-B53:01:01 on the other haplotype, however, is rare among Caucasians, but commonly found in West Africa. He produces two maps showing the geographical spread of my sort of haplotypes. One is most frequently found in Ireland; the other in Russia.
This makes sense. Although I was born in the US, I am about as genetically Irish as it is possible to be, the only potential exception being my father’s mother, who was adopted. My father once told me she was a Chechen, but he actually has no idea, and tends to change his story depending on which interesting nationalities happen to be in the news. According to my DNA, however, he may have been right.
Statistically speaking, I possess the 39th most common haplotype among European caucasians, alongside the 125th.
“So they’re not quite the commonest ones,” Marsh says.
“Let’s face it,” my wife says. “They’re pretty common.”