A 15-year-old Australian girl has become the first known transplant patient to change blood groups to take on the immune system of her organ donor.

The "one in six billion miracle", as it is being called, could lead to breakthroughs in organ-transplant treatment, doctors say, as normally, the immune system of recipients attacked the transplanted tissue of the recipient.

According to a report from World Science, the girl - Demi-Lee Brennan - received a liver from a donor when she was nine years old, after her own liver failed.

Her body changed from O negative to O positive, doctors say, after becoming ill while on anti-rejection drugs given to allow her immune system to accept the donated organ. Her new liver's blood stem cells, it is reported, then invaded her body's bone marrow to take over her entire immune system. She now no longer needs anti-rejection drugs.