Teen takes on donor's immune system

By medical reporter Sophie Scott and staff reporters
January 24, 2008

A 15-year-old Australian liver transplant patient has defied modern medicine by taking on her donor's immune system.

Demi-Lee Brennan had a liver transplant after she suffered liver failure. Nine months later, doctors at Sydney's Westmead Children's Hospital were amazed to find the teenager's blood group had changed to the donor's blood type.

Further tests revealed the stem cells from the donor liver had penetrated her bone marrow.

Dr Michael Stormon says he and his colleagues were even more surprised when they found the girl's immune system had almost totally been replaced by that of the donor, meaning she no longer had to take anti-rejection drugs.

"We consulted widely throughout the hospital and then looked at the medical literature and consulted colleagues around the world to see if anyone had seen this kind of thing before," he said.

"No-one had, so we were stunned and amazed."

Dr Stormon says his team is now trying to identify how the phenomenon happened and whether it can be replicated.

"That's probably easier said than done... I think it's a long shot," he said. "I think it's a unique system of events whereby this happened.

"We postulate there's a number of different issues - the type of liver failure that she had, some of the drugs that we use early on to suppress the immune system and also that she suffered an infection with a virus called CMV, or cytomegalovirus, which can also suppress the immune system."

Anti-rejection drugs, known as immunosuppresants, have significant side effects, including serious infections and toxic effects on organs.

Dr Stormon says doctors are trying to identify which patients could come off the treatment.

"They may not, like Demi, change their blood group and change their whole immune system and their bone marrow but there are a small percentage of patients who seem to get away with not needing immunosuppresion," he said.

"But the difficulty is trying to identify which ones you should stop immunosuppression on because there's always that fear and risk that over many months or years, rejection can still occur."

The case has been published in the New England Journal of Medicine.