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Bacteria from our guts have the tools to solve blood bank shortages

The discovery of a new enzyme system that can convert type A blood into type O blood could ease strain on universal donors and transform healthcare

We all need blood. While millions of people do donate regularly, patient access to blood supplies can be limited by blood type.

There are four distinct human blood types. Blood cells display complex sugars called glycans on their surfaces, and these vary in the individual sugars they contain and how they are linked together. The glycans you have on your blood cell surfaces determine your blood type. These glycans are recognized by your immune system, whose job it is to find and destroy intruders. This is why the glycans are often also referred to as “antigens,” molecules that can trigger an immune reaction in a person who does not naturally produce that substance. Put simply, type A blood cells carry the A antigen, type B cells carry the B antigen, type AB cells carry both, and type O cells carry neither.

When someone receives a transfusion, they can only receive blood cells their body is able to recognize. Because it lacks any cell-surface glycans, type O is considered a “universal donor” blood, because it does not trigger an immune response from A or B type patients. Type O blood is the most common in most countries, found in around 45 to 55 percent of people, but available supply is still not nearly enough to satisfy demand.

This is why blood drives are always looking for more type O donors - but what if there were a way to convert all blood types into type O, by removing those pesky glycans from the blood cell surfaces? Scientists working at the University of British Columbia (UBC) in Vancouver, Canada may have found a way. A group of biochemists led by Stephen Withers have found a simple enzymatic pathway that can be used to directly convert type A into type O blood. This study was led by post-doc Peter Rahfeld, who discovered the enzymes that work together to very efficiently remove the A antigen. 

The idea of using enzymes called glycosidases with this kind of sugar-removing activity in order to create universal donor blood is actually quite old. In the 1980s, a team of researchers led by Jack Goldstein and Lilian Reich at Cornell University Medical College and the Memorial Sloan-Kettering Cancer Center found that a well-known α-galactosidase enzyme – isolated from coffee beans – could be used to remove the sugar that defines type B blood cells. They also showed that a type B patient’s blood cells could be enzymatically treated and returned to their veins. This process created blood that could then be transfused into type A and type O humans, with no harmful side effects. The cells were able to carry oxygen in the normal way, maintain their correct shape, and survive for the normal expected lifespan of a blood cell.

Their technique of using enzymes to make type O blood would increase the amount of universal donor blood available. This early research was a huge breakthrough, but the technology never reached the clinic. 

Now a new technique help scientists this possible. Find out how in this video ....



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