A kidney transplant without the need for immunosuppressives for ever thereafter looks like a distinct possibility now.
In transplant, unless the organ comes from an identical twin, the body's reaction is to reject it as a foreign invader.
Since the world's first transplant more than 50 years ago, scientists have searched for ways to trick the body into accepting a foreign organ as its own. Immune-suppressing drugs that prevent organ rejection came into wide use in the 1980s. But they raise the risk of cancer, kidney failure and many other problems. And they have unpleasant side effects such as excessive hair growth, bloating and tremors.
But two separate techniques adopted in the US seem to offer a way out. In both the cases, the recipients have recovered without the need for the immunosuppressives. The results appear in the New England Journal of Medicine.
In the first study at Stanford University, a man who received his brother's kidney has gone for two years without drugs after his doctors tweaked his immune system with irradiation and antibody treatments.
He then received an infusion of his brother's blood cells. This combined treatment created a kind of "peacekeeping" immune cell, which appeared able to avert the attack on the foreign organ.
"The idea of getting off drugs holds tremendous appeal for patients," said the study's lead author, Professor John Scandling.
"So far, there is hope, but we still have a long way to go."
The second study was conducted at Massachusetts General Hospital.
Five patients were given treatment that partially destroyed their bone marrow and with it the white blood cells which cause rejection.
This bone marrow was then replaced with a bone marrow graft from the donor, and the kidney followed.
One of the five rejected the kidney, but the other four have so far been able to live with normal kidney function and without drugs - the longest for over five years.
"There's reason to hope these patients will be off drugs for the rest of their lives," said Dr. David Sachs of Massachusetts General Hospital in Boston, who led the research.
Eliminating the need for anti-rejection drugs is "a huge advance," said Dr. Suzanne Ildstad, a University of Louisville immunology specialist who had no role in the work.
"It still needs some fine-tuning so that everyone who gets treated gets the same consistent outcome ... It's not the holy grail of tolerance yet," she cautioned.
Sachs himself admitted that while the treatment was indeed promising, it won't solve the country's organ shortage problem. Nearly 98,000 people are on the waiting list, according to the United Network for Organ Sharing.
While most transplant units in the UK have managed to cut the dosage by about 50% in the last five years, the risk of side-effects remains, BBC reports.
Dr Robert Higgins, a specialist in renal transplantation, said while both studies were exciting, he had particular concerns about the one carried out in Massachusetts.
"While these early results are encouraging, the treatment involved in destroying the bone marrow can be life threatening, and there are other risks, such as the bone marrow graft trying to 'reject' the patient."
He added: "As in all parts of the world, the main problem in transplantation is the shortage of organs."