Scientists can convert blood type A into 0

Blood types A, B, AB or 0 are determined by molecules on the surface of red blood cells, called antigens. Type A blood has A antigens; type B has B antigens and type AB has both. Type 0 blood does not have antigens, and this is why it can be safely given to anyone (universal donor). However, types A, B and AB can only be infused into people with matching blood types. Otherwise, the body will produce antibodies to attack these red blood cells with antigens that they don’t recognize as their own.

For years, researchers could not find an enzyme that worked well enough to convert big quantities of blood in a cheap way. Peter R. and colleagues have discovered that a bacterium found in the gut, called Flavonifractor plautii, produces two enzymes that are capable to convert type A blood into type 0. 

How can this bacterium change type A blood into 0?

The only difference between type A and 0 blood cells is that type A have an additional sugar molecule (N-acetyl-galactosamine, or GalNAc) attached to their surface. GalNAc is just a fancy name of a sugar molecule in which a hydroxyl group (OH) has been replaced with an amino group (NH2). If this GalNAc is removed from type A blood, it becomes type 0. Because microbes that attach to the gut lining are capable to digest sugars, Peter R. and colleagues started looking at the human gut for bacterial enzymes that could use for this purpose.

The researchers show that these two enzymes had high activity and specificity. Thus, they are a promising candidate for a cost-efficient way to convert blood type A into 0. Still, some features need to be investigated: safety and efficiency in different blood samples.