Previous research by Thomas P. Stossel of Harvard Medical School and his colleagues indicated that chilling platelets caused some of the protein receptors on their surfaces to cluster together. When infused into a patient, immune cells known as macrophages detect these clusters and ingest the platelets. In the new work, the scientists hypothesized that if the clusters could be disguised from macrophages, chilled platelets could continue functioning as well as non-refrigerated platelets do. To do this, the scientists added a sugar to the platelet solution. Known as UDP galactose, it conceals the clusters on the chilled platelets that elicit an immune response. In test-tube experiments, platelets treated with the sugar avoided detection by macrophages even after having been stored for 12 days. In fact, sugar-treated refrigerated platelets injected into mice were still detectable after 24 hours, whereas levels of untreated chilled platelets diminished rapidly after the transfusion.
Because UDP galactose is already present in human cells and body fluids, the researchers are optimistic that this technique would not pose additional health hazards to patients receiving platelet donations. If judged to be safe and effective in humans, sugar-coating the platelets should help ease shortages. "As the population gets older, we need more and more donations, and the number of younger donors is shrinking," notes study co-author Karin Hoffmeister of Brigham and Women's Hospital. "The blood banking industry loses a significant amount of money by throwing these bags of platelets away."