Scientists have found a way to change types A and B human blood into type O, the universal-donor blood that can be given to anyone. A- and B-type blood cells have identifying sugar molecules on them. A team led by Dr. Henrik Clausen, of Harvard University and the University of Copenhagen, isolated enzymes that trim off those molecules. "They can clip off, very specifically, just that one sugar residue," he explains, adding that the rest of the long sugar chain is very similar to what is on blood group O red cells. "It's sort of a scissor trimming of the red cell surface, so the immunogenic sugars are removed, the ones you don't have." That prevents an immune reaction against the wrong blood type.

Clausen explains that donated blood would be mixed with the enzyme, and shaken for an hour. "Then you basically wash the red cells [so] the sugar you clipped off washes off, and the enzyme you put in washes out as well." Then the blood is put back into the storage solution, and is ready to be used in any patient, without having to type their blood.

If the process is found to be safe and effective on a large scale, it will make a small but important difference in the blood supply, according to Dr. Richard Benjamin, chief medical officer at the American Red Cross. "This product will provide us with more group O blood, it will help to some extent with shortages, and it will help in our efforts to supply hospitals and patients and their needs." But he stresses that it is not a panacea. "We still need the donors to come in!"

Details of the newly isolated enzymes appear in the current issue of the journal Nature Biotechnology.