Blood types A, B, and AB can be efficiently converted to type O, which is safe to give to anyone, says an international team of researchers.
The scientists identified bacterial proteins that can quickly convert one blood type to another by clipping away sugar molecules on red blood cells.
The find may create a universally safe supply of blood and may help end shortages, since mismatched blood transfusions can quickly cause death.
Deadly Mismatches
Under the ABO system discovered in 1900, blood is classified into four groups based on the presence or absence of complex sugar molecules on the surfaces of red blood cells.
"Group A has an enzyme that puts a sugar molecule on the end," explained Geoffrey Daniels, a transfusion scientist at the University of Bristol in England.
"Group B also has an extra sugar molecule, different from that on group A, at the end of its structure," he added. "But group O has neither kind of sugar molecule."
People naturally create antibodies to the sugars they lack. So people with blood type A naturally have antibodies to the blood plasma from type B, and vice versa.
If people get blood transfusions of the wrong type, their antibodies attack the foreign sugars, mounting a vigorous and oftentimes deadly immune response.
"The blood cells clump together as a consequence of the antibodies acting like a glue between cells, and thus blood gets very thick," said Steve Withers, a bioorganic chemist at the University of British Columbia, Canada.
"The red blood cells can explode."
People with blood type O, however, are considered universal donors, since their blood cells contain no sugars to attack. (Related: "Umbilical Cord Blood: The Future of Stem Cell Research?" [April 6, 2006].)
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