Stanford University researchers report success in two patients with a new approach that may free kidney transplant recipients of the need to take a lifelong course of immunosuppressive drugs to prevent rejection.

Dr. Samuel Strober, professor of immunology, said that after the transplant, the kidney recipient receives multiple small doses of radiation targeted to the immune system combined with a drug to reduce the number of cells capable of an immune attack.

In their four-patient study, the researchers then injected blood stem cells from the kidney donor into the recipient. The stem cells made their way to the recipient's bone marrow where they produced new blood and immune cells that mixed with those of the recipient.

The researchers said they then monitored the recipient's new hybrid immune system looking for a mixture of cells from both the recipient and the donor. These cells were then tested in the laboratory. At the point that the mixed cells did not attack cells taken from the donor, the researchers began slowly weaning the patient off immunosuppressive drugs.

Strober said the study asks two questions: Can you get patients off the immunosuppressive drugs and, if so, for how long?

"We feel we can answer yes to the first question," Strober said, adding that so far, two of the four patients in the study are completely free of drugs, with another still tapering off.

Strober noted that these powerful drugs leave kidney recipients open to infection and increase the risk of heart disease or cancer later in life. Research results from four patients in the groundbreaking study will be presented April 28 in Washington, DC, at the American Transplant Congress by Maria Millan, MD, transplant surgeon at Stanford Hospital & Clinics and assistant professor of surgery. The work is also scheduled to be published in the journal Transplantation May 15.

Results of the study are scheduled to be presented at next week's joint meeting of the American Society of Transplantation and the American Society of Transplant Surgeons.

Other sources: Stanford University