Blood is always in demand, and not just by vampires. Blood transfusions mean the difference between life and death when people suffer traumatic injuries, or undergo major surgery.
But there’s always been a problem with transfusions: people don’t all have the same blood type, and giving someone the wrong blood type is worse than giving them no blood at all.
That may be about to change, though: scientists have developed a method of converting the different types of human blood into a neutral type that can be given to anyone.
First, a reminder of what exactly blood is, aside from the reason Dracula doesn’t drink…wine.
The main constituent of blood is plasma, a yellowish fluid that’s primarily water but also contains proteins, sodium, potassium, calcium chloride, carbonate, bicarbonate, sugar, hormones, enzymes, fats, amino acids and waste products such as urea.
Blood is red because of the red blood cells suspended within the plasma: five million per cubic millimetre. The cells are red because they contain a substance called hemoglobin, which combines with oxygen as it passes through the lungs. (It’s blue-red before that happens and bright red after, which is why blood from veins and blood from arteries aren’t the same colour.)
There are also white blood cells (5,000 to 10,000 per cubic millimetre), whose job is to protect you from infection. Some eat bacteria; some stimulate inflammation; some only respond to certain infections and allergies. Finally, there are the much smaller platelets (200,000 to 300,000 per cubic millimetre), which promote clotting.
If everybody’s blood has pretty much the same constituents, why can’t you mix and match it freely? Because the cell walls of red blood cells contain complex sugars which can trigger an immune response in someone else’s body.
Specifically, people with type A red blood cells carry antibodies that will attack and kill blood cells carrying type B sugars, while people with type B blood cells carry antibodies that will attack and kill blood cells carrying type A sugars. People with AB blood can accept both kinds of blood, but can only donate to someone else of type AB. And then there are people with type O blood, who can give blood to anyone, but can only accept type O blood: their body rejects all other kinds. Type O blood is always in great demand at blood banks, but always in short supply—it’s rare.
Now researchers at the University of Copenhagen, led by Henrik Clausen, have discovered enzymes that can chop the A and B sugars off of red blood cells. With those sugars gone, antibodies don’t react to the blood cells—and blood type no longer matters.
This isn’t the first attempt to come up with a method of neutralizing blood type, but previous enzymes haven’t worked very well. In the 1080s a team in New York discovered an enzyme from green coffee beans that could remove the B antigen, but it proved too inefficient to be practical.
According to Clausen, that’s because that enzyme was identified using simple sugars that didn’t actually behave the way the sugars on red blood cells behave. His team used the actual complex sugars found on the cells, with much better results.
The enzyme they found which removes the B antigen is from a gut bacterium called Bacteroides fragilis, and the enzyme which removes the A antigen is from a bacterium called Elizabethkingia meningosepticum, which occasionally causes infections. These enzymes are far more efficient than anything found before: the enzyme from the B. fragilis bacterium is used up at a thousandth of the rate of the enzyme found in coffee beans.
ZymeQuest, a company based in Beverly, Massachusetts, has licensed the enzymes and is developing a machine that can treat eight units of blood in 90 minutes. The processed blood is in clinical trials now, and if it everything pans out, the blood-processing machines could be on the market in Europe by 2011, and in the U.S. a few years later.
Considering it’s estimated an error in blood type is made once in every 15,000 transfusions, success can’t come soon enough.
