Organ-transplant advancements may eliminate immune system therapy

Researchers have discovered a way to transplant kidneys so that the patients don't have to remain on immune-suppressing drugs for their rest of their lives.

The procedure, which creates a hybrid immune system from patient and donor, has only been tried on four patients, but it appears to work well enough that it would allow donations from living donors who aren't related or closely matched with recipients.

Dr. Maria Millan, a transplant surgeon at Stanford Hospital and Clinics and an assistant professor at Stanford University, described the work Sunday before the American Transplant Conference meeting in Washington, D.C. The research is to be published next month in the journal Transplantation.

Successful organ transplantation demands that the patient's immune system be heavily suppressed with powerful drugs to keep it from attacking the new organ's foreign cells.

"Transplantation is a life-saving procedure, but the price is the lifelong use of immune suppressing drugs," said study leader Dr. Samuel Strober, a professor of immunology at Stanford. The drugs can leave patients at greater risk for infection and increase their risks of cancer and heart disease later in life.

The Stanford scientists are among many working to continue protecting transplanted organs while avoiding the unwanted side effects of immune-suppressing drugs.

While other transplant specialists have had some success with similar techniques, all previous experiments have used patients and donors who were perfectly matched, usually siblings.

"We're trying to address two questions: can you get patients off the drugs, and, if so, for how long?" Strober said. "We feel that we can answer yes to the first question," he added, with two of the four patients completely independent of the drugs and a third off one drug but still tapering off others. The fourth patient experienced severe organ rejection and must remain on traditional drugs.

"We need to pursue this route because we've topped out on what we can do with drugs," Millan said, although many researchers continue searching for new drugs that can more safely switch off the immune system.

The kidney transplants started out with the usual grafting procedure, accompanied by drugs to knock down the immune system. But in the next step, the recipients got many small doses of radiation targeted to their immune systems, coupled with a drug that reduced the number of cells capable of mounting an immune attack.

Then the team injected blood stem cells from the kidney donor into the recipient. Those stem cells migrated to the patient's bone marrow, where they produced new blood and immune cells that mixed with those of the patient. After this step, the patient's immune cells recognized the donated organ as friend rather than foe.