Besides the ethical concerns of stem cell therapy (see "stem cell controversy"), there is a technical problem of graft-versus-host disease associated with allogeneic stem cell transplantation.
A common complication of allogeneic stem cell transplantation, graft-versus-host disease, occurs when the body's immune system flares in response to the donated stem cells.
However, even for attenuated patients, it is a major intervention with not insignificant mortality risks and potential for life-threatening or altering complications such as graft-versus-host disease.
In particular, they believe a common complication of transplantation, graft-versus-host disease, could be at play because it involves newly transplanted donor cells attacking the transplant recipient's body.
He has also advanced understanding other complex immune effects of transplants in humans, like graft-versus-host disease and posttransplant immune deficiency.
Even if there is a good match at these critical alleles, the recipient will require immunosuppressive medications to mitigate graft-versus-host disease.