An Australian girl spontaneously switched blood groups and adopted her donor's immune system following a liver transplant in the first known case of its type.

Demi-Lee Brennan was aged nine and seriously ill with liver failure when she received the transplant.

Nine months later it was discovered that she had changed blood types and her immune system had switched over to that of the donor after stem cells from the new liver migrated to her bone marrow.

She is now a healthy 15-year-old, Michael Stormon, a hepatologist treating her, said. Stormon said he had given several presentations on the case around the world and had heard of none like it.

Doctors are interested to know if the case could have other applications in transplant surgery, where rejection of donor organs by the recipient's immune system is a major hurdle.
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The liver is one of the few organs that could do this I would think - i mean, before you're born most of your blood is produced in your liver, i can see stem cells continuing to hang out there.

My MAIN issue is that if the majority of this girl's immune system is now descended from these transplanted stem cells, how is she not getting graft-vs-host disease, where her new immune system attacks her ENTIRE body except for the transplant?

The human body is an amazing thing.
But one question..............for a transplant shouldn't the organ and the patient be the same blood type???

No, that only matters for certain specific organs that express the blood type antigens on their cell surfaces, like the kidneys (and blood of course). For most organs, what matters is the MHC (Major Histocompatability Complex) proteins, a series of many genes and protein products with a great deal of variability from person to person. They perform the job of presenting viral antigens to the immune system if a cell is infected, and do other jobs on immune system cells, but their immense variability makes them the main culprit of transplant rejection. Any given organ donor only has a one in ten thousand chance of exactly matching your MHC. Therefore most transplant patients get sub-optimal matches that are prone to rejection.

It turns out that if you transplant an immune system (usually through bone marrow though it seems to have happened with a liver here) these aren't so important - what matters is the HLA (Human Leukocyte Antigen) proteins that are used in certain immune system cells. Since maturing immune cells acclimate themselves to your body to ensure they do not attack it, an MHC mismatch will not be a big deal there, but an HLA mismatch runs the risk of the new immune system deciding that your ENTIRE BODY is foreign and must go (it's called "graft vs host disease"). I'm just wondering if this patient happened to receive a matched HLA set, or if they are running the risk every day of developing graft vs host.