Research presented to the International Congress of The Transplantation Society in Miami, Florida, showed how some patients' immune systems can be fooled into believing they do not need anti-rejection drugs.

BBC: 'Drug-free' transplant hope

"The Transplantation Society is opposed to the use of executed prisoners, because without transparency of practice and oversight there is a concern that the escalating need for organs has propelled an escalating need for executions, " says Dr. Francis Delmonico, medical affairs director of the society, located in Montreal.

FORBES: Magazine Article

Mr Keith Rigg, a transplant surgeon and vice president of the British Transplantation Society, said that the work was "interesting", but had not yet convinced him that it could work in humans.

BBC: Frozen liver transplant success

Professor John Fabre, a former president of the British Transplantation Society, said that passing opt-out legislation in Spain was not the reason why the country had achieved a high donation rate.

BBC: Deadline for public to have say on organ donation law