An Australian girl has become the world's first known organ transplant patient to change blood types and take on the immune system of her organ donor, allowing her to stop taking anti-rejection drugs.
Doctors, who detailed the finding in the latest edition of The New England Journal of Medicine, are calling the unexpected development a "miracle."
Demi-Lee Brennan, now 15, received a donor liver from a young boy when she was nine years old. About nine months later, she became ill with an infection while on drugs to avoid rejection of the organ by her body's immune system.
It was then that her body changed blood group from O negative to O positive. At the same time, her new liver's blood stem cells invaded her body's bone marrow to take over her entire immune system.
Within 17 months of the surgery, she was able to go off her anti-rejection drugs. It's been three and a half years and she hasn't needed the drugs since.
"It's like my second chance at life," Brennan told a news conference at Sydney's Westmead Children's Hospital on Friday. "It's kind of hard to believe."
Doctors the hospital said they had no explanation for Brennan's recovery.
Michael Stormon, a paediatric hepatologist who treated Brennan says it's possible that the infection she suffered may have given the stem cells from her donor's liver the chance to proliferate in her bone marrow, where blood cells develop.
"In effect she had had a bone marrow transplant. The majority of her immune system had also switched over to that of the donor," he told French news agency AFP from the Children's Hospital at Westmead.
Normally, the immune system of organ recipients attacks the transplanted tissue as a foreign body. That rejection response is normally treated with a combination of immunosuppressive medications that need to be taken for the rest of an organ recipient's life.
Stormon says he has given several presentations on the case around the world and has heard of none like it. But he says if they figure out the mechanism of how her body made the change, it could revolutionize organ transplant surgery.
"The holy grail of transplant medicine is immuno-tolerance. She exemplifies that this can occur."
Stuart Dorney, the hospital's former transplant unit head, said his team now has to go back over everything that happened to Brennan and see if it can be replicated. But he already has a theory as to how it happened.
"We think because we used a young person's liver and Demi-Lee had low white blood cells, that could have been a reason," he told the Daily Telegraph newspaper.
