In the months after their transplants, the patients in the study were treated with immunosuppressive drugs, but four out of five of them were able to discontinue those drugs between 9 and 14 months after surgery, and their new kidneys have been functioning well in the years since.

"I think it's quite exciting," Magee says. "It shows what's possible."

The researchers' approach could make transplants more feasible for people whose immune systems are already compromised by conditions like HIV, according to Yasir Qazi, medical director of the kidney and pancreas transplant program at the University of Southern California. (Qazi was not involved in the work.) Sykes says that the approach could potentially be used to treat autoimmune diseases such as type 1 diabetes. "It could have huge benefits," she says.

Although immunosuppressive drugs have revolutionized transplant medicine, they can increase the risk of cancer and heart disease. "Immunosuppression is great, because it makes kidneys work, but it's bad because it has lots of side effects," Magee says. "Some people say that in many ways, you're trading one disease for another. You still have to take lots of medicine and see a doctor."

The protocol developed by Sykes and her colleagues initially requires heavier drug treatment than that required with the standard kidney-transplant procedure, to allow the recipient's body to accept donated bone marrow as well as a donated kidney. But, she points out, the patient is only on the drugs for a limited time.