If you receive blood from a “positive” donor, then your own antibodies may react with the incompatible donor blood cells, triggering a further response from the immune system. If a particular high-prevalence antigen is missing from your red blood cells, then you are “negative” for that blood group. If you lack one that 99.99 percent of people are positive for, then you have very rare blood. If you lack an antigen that 99 percent of people in the world are positive for, then your blood is considered rare. Some 160 of the 342 blood-group antigens are “high-prevalence,” which means that they are found on the red blood cells of most people. It is the presence or absence of particular antigens that determines someone’s blood type. On the surface of every one of our red blood cells, we have up to 342 antigens-molecules capable of triggering the production of specialized proteins called antibodies. It would be straightforward if we all had the same blood. Hence the hundreds of millions of people flowing through blood-donation centers across the world, and the thousands of vehicles transporting bags of blood to processing centers and hospitals. If we lose a lot of blood in surgery or an accident, we need more of it-fast. Red blood cells carry oxygen to all the cells and tissues in our body. In 50 years, researchers have turned up only 40 or so other people on the planet with the same precious, lifesaving blood in their veins. Very few people in the world knew his blood type did-could-exist. Surely it was impossible for this man seated beside her to be alive, let alone apparently healthy? But when she read the details closely, her eyes widened. The nurse in Annemasse, France, could tell from the label on the blood bag destined for Paris that this blood was pretty unusual. It was quicker that way: If the man donated in Switzerland, his blood would be delayed while paperwork was filled out and authorizations sought. "Now we are in the process of introducing it in the clinic and aim to find out what this exciting protein does and the consequences of the fact that so many of us don't have it," concludes Martin L Olsson.His doctor drove him over the border. The finding makes it possible finally to determine also the Xga blood type using genetic typing/methods. The lab experiments showed that a small variation close to the XG gene prevents the transcription factor GATA1 from binding to the DNA, which is why the Xg protein cannot be expressed in the red blood cells in some people. Then my colleagues took over to confirm my findings through experiments in a lab environment," says Mattias Möller. "I sat down at my computer and analysed and compared results from previous major studies, partly using my own tools, to solve the problem. "We used a bioinformatic strategy to find the underlying genetic cause," says doctoral student Mattias Möller, who used to work in the tech industry before making a switch to become a physician and blood researcher. "We enjoy solving old mysteries where others have failed, so we combined computer-based analyses with laboratory experiments," explains Martin L Olsson, professor at Lund University and medical consultant at the Nordic Reference Laboratory for Blood Group Analysis, who conducted the study.Īlthough this blood type was the first to be linked to a specific chromosome in humans (sex chromosome X), Xg is the last blood type system to surrender its secret and thus be included in modern genetic testing. The Xga blood type was discovered in New York back in 1962, but it wasn't until now that researchers in Lund managed to figure out why a large part of the population lacks Xga. Furthermore, the protein's function is still unknown. A third of all men and a tenth of all women lack the Xg protein that carries the mysterious blood type Xga on their red blood cells, i.e. In practice, it's actually only one system - the Xg system - that has continued to elude physicians and researchers over the years. This is the case for the majority of our 36 systems, including ABO and Rh. However, for the DNA tests to work, the genetic cause of each blood type system must be known. This makes it difficult to determine the patient's own blood type. Modern technology is particularly important for patients who have received large amounts of blood or those who need blood often, as their blood becomes a mixture consisting of several different donors. Over the past ten years, researchers have developed methods to determine many of our blood types using DNA technology rather than by red blood cells. However, other blood types can also cause problems. The well-known blood group systems ABO and Rh are prioritised as they are clinically the most important. The reason is that you want them to match in order to reduce the risk of side effects. In case of a blood transfusion, it is important to know the blood type of both the donor and the patient.
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