O negative donors who are CMV negative are known as Heroes for Babies at the Red Cross because it is the safest blood for transfusions for immune deficient newborns. Learn more about how you can be a Hero for a Baby. Due to the its versatility for transfusions, it is in high demand. In an emergency, it is the blood product of choice. For example, just one car accident victim can require up to units of O neg. Meeting the demand for O negative blood is always a priority for the Red Cross.
O negative is the first blood supply to run out during a shortage due to its universality. O positive donors who are CMV negative are known as Heroes for Babies at the Red Cross because it is the safest blood for transfusions for immune deficient newborns. The risk of reaction is much lower in ongoing blood loss situations and O positive is more available than O negative.
It turned out that some primate species had blood that mixed nicely with certain human blood types. But for a long time it was hard to know what to make of the findings. Type A blood might have evolved more than once.
The uncertainty slowly began to dissolve, starting in the s with scientists deciphering the molecular biology of blood types. They found that a single gene, called ABO, is responsible for building the second floor of the blood type house. The A version of the gene differs by a few key mutations from B. People with type O blood have mutations in the ABO gene that prevent them from making the enzyme that builds either the A or B antigen. Scientists could then begin comparing the ABO gene from humans to other species.
Gibbons and humans both have variants for both A and B blood types, and those variants come from a common ancestor that lived 20 million years ago. But the evidence that scientists have gathered so far already reveals a turbulent history to blood types.
In some lineages mutations have shut down one blood type or another. Chimpanzees, our closest living relatives, have only type A and type O blood. Gorillas, on the other hand, have only B. And even in humans, scientists are finding, mutations have repeatedly arisen that prevent the ABO protein from building a second storey on the blood type house. These mutations have turned blood types from A or B to O.
Bombay puzzle Being type A is not a legacy of my proto-farmer ancestors, in other words. Surely, if my blood type has endured for millions of years, it must be providing me with some obvious biological benefit. Otherwise, why do my blood cells bother building such complicated molecular structures?
Yet scientists have struggled to identify what benefit the ABO gene provides. The most striking demonstration of our ignorance about the benefit of blood types came to light in Bombay in If A and B are two-storey buildings, and O is a one-storey ranch house, then these Bombay patients had only an empty lot. Since its discovery this condition — called the Bombay phenotype — has turned up in other people, although it remains exceedingly rare.
Those with the Bombay phenotype can only accept blood from other people with the same condition. Even blood type O, supposedly the universal blood type, can kill them. Some scientists think that the explanation for blood types may lie in their variation.
Doctors first began to notice a link between blood types and different diseases in the middle of the 20th Century, and the list has continued to grow. From Greenwell I learn to my displeasure that blood type A puts me at a higher risk of several types of cancer, such as some forms of pancreatic cancer and leukaemia. On the other hand, people with other blood types have to face increased risks of other disorders. People with type O, for example, are more likely to get ulcers and ruptured Achilles tendons.
These links between blood types and diseases have a mysterious arbitrariness about them, and scientists have only begun to work out the reasons behind some of them. For example, Kevin Kain of the University of Toronto and his colleagues have been investigating why people with type O are better protected against severe malaria than people with other blood types.
More puzzling are the links between blood types and diseases that have nothing to do with the blood. Take norovirus. This nasty pathogen is the bane of cruise ships, as it can rage through hundreds of passengers, causing violent vomiting and diarrhoea.
It does so by invading cells lining the intestines, leaving blood cells untouched. The solution to this particular mystery can be found in the fact that blood cells are not the only cells to produce blood type antigens.
They are also produced by cells in blood vessel walls, the airway, skin and hair. Many people even secrete blood type antigens in their saliva. Noroviruses make us sick by grabbing onto the blood type antigens produced by cells in the gut.
That would explain why our blood type can influence which norovirus strains can make us sick. It may also be a clue as to why a variety of blood types have endured for millions of years.
Our primate ancestors were locked in a never-ending cage match with countless pathogens, including viruses, bacteria and other enemies. Some of those pathogens may have adapted to exploit different kinds of blood type antigens. The pathogens that were best suited to the most common blood type would have fared best, because they had the most hosts to infect.
But, gradually, they may have destroyed that advantage by killing off their hosts. Meanwhile, primates with rarer blood types would have thrived, thanks to their protection against some of their enemies.
As I contemplate this possibility, my type A blood remains as puzzling to me as when I was a boy. I realise that the reason for my blood type may, ultimately, have nothing to do with blood at all. This article was originally published by Mosaic, and is reproduced under a Creative Commons licence. Mosaic Future Disease. Why do we have blood types? Type O is more prevalent in Africa and other parts of the world that have high burdens of malaria, suggesting that blood type carries some sort of evolutionary advantage.
In this particular case, the advantage appears to be that cells infected with malaria don't stick well to type-O or type-B blood cells, Cserti-Gazdewich said. Malaria-infected blood cells are more likely to stick to cells with the A sugar and to form clumps known as "rosettes," which can be deadly when they form in vital organs, such as the brain.
As a result, people with type O get less sick when they're infected with malaria, according to a study in the Proceedings of the National Academy of Sciences. On the other hand, people with type-O may be more prone to other diseases. For example, they are known to be more susceptible to Helicobacter pylori, a bacterium that causes ulcers, Klein said. But research hasn't yet shown whether that or some other disease explains why humans still have blood types.
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