In the early 1950's, a 66-year-old woman with colon cancer received a blood transfusion - but she suffered a severe rejection of the transfused blood. When writing the case study, the medical journal Revue D'Hématologie identified her only as "Patient Vel."
It was determined that Mrs. Vel had developed a potent antibody against some unknown molecule found on the red blood cells of most people in the world—but not found on her own red blood cells. But the molecule was unknown, nobody could find it. A blood mystery began, and, from her case, a new blood type, "Vel-negative," was described in 1952.
Soon it was discovered that Mrs. Vel was not alone. It is estimated that over 200,000 people in Europe and a similar number in North America are Vel-negative, about 1 in 2,500. For these people, successive blood transfusions could easily turn to kidney failure and death. So, for sixty years, doctors and researchers have hunted for the underlying cause of this blood type.
Now a team of scientists from the University of Vermont and France has found the missing molecule—a tiny protein called SMIM1—and the mystery is solved. "Our findings promise to provide immediate assistance to health-care professionals should they encounter this rare but vexing blood type," says University of Vermont's Bryan Ballif. Last year, Ballif and Arnaud identified the proteins responsible for two other rare blood types, Junior and Langeris, moving the global count of understood blood types or systems from 30 to 32. Now, with Vel, the number rises to 33. The little protein didn't reveal its identity easily. "I had to fish through thousands of proteins," Ballif says. And several experiments failed to find the culprit because of its unusual biochemistry—and pipsqueak size. But he eventually nabbed it using a high-resolution mass spectrometer funded by the Vermont Genetics Network. And what he found was new to science. "It was only a predicted protein based on the human genome," says Ballif, but hadn't yet been observed. It has since been named: Small Integral Membrane Protein 1, or SMIM1.
Next, Lionel Arnaud of the French National Institute of Blood Transfusion
and the team in France tested seventy people known to be Vel-negative. In every case, they found a deletion—a tiny missing chunk of DNA—in the gene that instructs cells on how to manufacture SMIM1. This was the final proof the scientists needed to show that the Vel-negative blood type is caused by a lack of the SMIM1 protein on a patient's red blood cells.
Today, personalized medicine— where doctors treat us based on our unique biological makeup—is a hot trend. "The science of blood transfusion has been attempting personalized medicine since its inception," Ballif notes, "given that its goal is to personalize a transfusion by making the best match possible between donor and recipient.
"Identifying and making available rare blood types such as Vel-negative blood brings us closer to a goal of personalized medicine. Even if you are that rare one person out of 2,500 that is Vel-negative, we now know how to rapidly type your blood and find blood for you—should you need a transfusion."