Every year, 4,500 Americans die waiting for a kidney transplant. It's not just because there aren't enough donors—part of the problem is that donors need to be compatible to prevent the recipient's body from rejecting the new kidney. They need the right blood type, but they also have to have the right combination of six antigens--molecules on a cell that have the capacity to trigger an immune response. Any two random people have a one in 100,000 chance that all six antigens will match, and even then it's not a guarantee that the kidney won't be rejected.

Fifteen years ago, researchers from the Johns Hopkins University School of Medicine started developing a technique to quiet the recipient's immune system, making even incompatible donors a match. Now, after an eight-year study and evaluating thousands of patients, they have proof that this immune-quieting method works better than the alternatives and is saving lives, which could make it more widespread. The researchers published a study today in the New England Journal of Medicine.