Magen David Adom - already suffering from a shortage of blood for surgery due to the holiday - is worried that publicity about Danish researchers who managed to turn types A, B and AB blood into type O will further reduce the number of blood donations in Israel. "It will take several years until the discovery will increase the supply of type O blood, which can be given to any patient," MDA blood services director Prof. Eilat Shinar told The Jerusalem Post on Wednesday. "It is not artificial blood; even if they manage to take non-O blood and turn it into type O, you still need human blood as the raw material. Blood donations must continue," Shinar said. Dr. Henrik Clausen of the University of Copenhagen and colleagues described Sunday in the April 1 on-line issue of Nature Biotechnology two previously unknown enzymes - small amounts of which are capable of efficiently removing the A and B agglutinogen. Type O, which lacks these components, is the "universal donor" type that can be given to people with A, B, AB and of course O type blood. Blood types are based on the kind of molecule called agglutinogen, an antigen found on the surface of red blood cells. Type O does not react with other types when mixed, but types A, B, or AB can clump together when mixed. In the '80s, scientists started to test the idea of eliminating the surface proteins on red blood cells to create universal blood cells. Seven years ago, US researchers demonstrated that type B red blood cells could be turned into type O cells, which then survive normally when given to type A and O individuals. The process utilized an enzyme from green coffee beans that could remove the B antigen from red blood cells. It proved too inefficient and impractical due to the large amount of enzymes needed for this conversion and was thus regarded as impractical. In the article, Clausen and colleagues wrote: "The enzymatic conversion processes we describe hold promise for achieving the goal of producing universal red blood cells, which would improve the blood supply while enhancing the safety of clinical transfusions." The Danish scientists screened bacteria and fungi for stronger enzymes than those in coffee beans. "The diversity you get in the bacterial kingdom is much higher," wrote Clausen, who focused on two enzymes. One is from a bacterium in the gut called Bacteroides fragilis, which removes the B antigen, and the other, Elizabethkingia meningosepticum, works on the A antigen. The Danes are collaborating with a Massachusetts company called ZymeQuest, which plans clinical trials to determine whether the enzyme-converted blood is safe and effective. If it is, the product will be in great demand by blood banks around the world. Type A and B antigens, which give blood groups their name, are sugars carried on the surface of red blood cells. Human red blood cells can carry one of these antigens, both, or neither; giving four blood groups: A, B, AB and O, respectively. Receiving mismatched blood can cause a life-threatening complication, and errors are made in one out of in every 15,000 transfusions in the US. Shinar noted that in most populations around the world, 35 percent to 40% have type A, 17% have type B, 35% to 40% have type O and the rest AB, thus conversion to O would be a boon. "We hope the Danish researchers will succeed, but they have not been able to change the RH factor (+ and -), which cannot be given to people with the opposite factor. The A and B antigens are sugars that leave the red blood cell. An enzyme cuts them and turns them into O. In RH, however, there is not a sugar but a protein that is located in the wall of the cell and not inside." Because so many Israelis are away on vacation, either inside the country or abroad, the number of blood donors is currently way down, causing MDA to limit the supply to hospitals. Shinar asks good-hearted donors to donate. On Friday, all MDA stations will be open specially for donations. More information is available from the toll-free number 1-800-400-101 or via the Web site at www.mdais.org.