Scientists alter blood type with gut microbes

In 2018, the American Red Cross announced that there was an urgent shortage of blood in the nation’s blood banks. Life-saving transfusions rely on gracious donors to fill up the reserves. Unfortunately, humans can’t just receive random units of blood.

Of the four blood types (A, B, AB, and O) almost any patient can receive type O during a transfusion. Meanwhile, type A can only be given to patients with type A blood—a much smaller portion of the population. Now, scientists have found a way to convert type A blood to type O. If clinical trials are successful, this discovery could double the world’s universal blood supply almost instantly.

Type and Cross

Each of the four blood types is classified based on the kind of surface antigens it possesses or lacks. These tiny sugar molecules serve as markers for the body’s immune system. Type A blood and type B have different antigens while type AB has both. What makes type O blood so valuable is the fact that it doesn’t have any surface antigens.


When a person receives the wrong type of blood, the immune system detects the presence of the foreign antigens. For example, a patient with blood type A who receives type B would have a reaction because of antigens in the donated blood. This adverse effect is known as a hemolytic reaction and can cause symptoms such as fever, fainting, itching, and shortness of breath.

Regardless of a person’s blood type, when receiving a donation of type O blood, the immune system won’t find any antigens to attack. In situations where hospitals can’t check a person’s blood type before giving a transfusion, such as in an emergency, type O blood can be administered with relatively low risk.

Thanks to the Gut

Scientists from the University of British Columbia found a way to strip the surface antigens off type A blood. This process effectively transforms it to type O, making it far more useful.

Published in the Nature Microbiology journal, the research promises to make a significant impact on the nation’s blood supply.

While the idea of stripping away antigens sounds like something that a tool like CRISPR can accomplish, the team found a much more natural method. Their source: the human gut. There, the intestinal lining features sugars similar to those found on blood cells. During digestion, bacteria found in feces strip those sugars to fuel the process.

The team was able to isolate this enzyme and use it to convert type A to type O blood successfully. The method seems to be as economical as it is effective since the bacterial enzymes could be grown quickly in a lab. Moreover, the technique was 30 times more efficient than any other method currently known.

While this discovery is undoubtedly a breakthrough, it will likely be several years before it is put into action nationwide. The technique will need to go through a clinical trial to ensure its safety first. However, if that goes well, the news will hopefully prompt a much-needed boost for the nation’s blood banks.

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