Doctors repaired the damaged skull of a Russian noble using a segment of bone taken from a dog.
Physicians began to graft animal tissues onto humans with some regularity. Over the next 20 years, doctors experimented with transplanting organs from pigs, goats, lambs and monkeys onto people.
Peter Medawar found that animals exposed to foreign tissues whilst embryos don't reject them. MacFarlane Burnet postulated that this is because the immune cells learn very early to accept whatever tissue is in the body and to attack those that arrive later in development. Medawar and Burnet won a Nobel Prize in 1960 for their discoveries.
Surgeon Joseph Murray performed the world's first successful organ transplant. Researchers began to develop immune suppressant drugs to prevent organ rejection.
Physicians again began to experiment with xenotransplants, focusing mainly on transplanting chimpanzee kidneys into humans.
James Hardy attempts the first cardiac xenotransplant, using an heart from a chimp. Researchers are learning more about the cause of hyper-acute rejection. They discover that human blood contains natural antibodies that, when encounter foreign tissue, will trigger a chain reaction to destroy it.
The first clinical trial report was released on the use of nerve cells from foetal pigs to treat a twelve patients with Parkinson's disease. The patients showed marked clinical improvement. Other researchers experimented with wrapping animal cells in capsules that prevent immune cells from destroying them.
An infant born prematurely with a malformed heart receives a heart from a baboon. The baby lives for 3 weeks (longer than any previous precipitant). However, the baby rejects the heart due to blood type incompatibility.
Researchers at Massachusetts General Hospital discover a particular sugar on the surface of pig cells provokes the attack of the human's natural antibodies. They realise that if scientists can genetically engineer pig's cells not to produce this, humans have a better chance at accepting the transplanted organ.
Jeff Getty receives a baboon bone marrow transplant in the hope that the immune cells in the baboon will replace those lost by Getty due to the AIDS virus. The baboon cells (which are naturally resistant to HIV) only functioned for a short period of time. However, Getty remains healthy and is alive today.
Scientists continue to investigate how pre-treating transplant recipients with marrow taken from the donors might create immune systems that contain cells from both animals and humans.
Researchers at the National Institutes of Health (NIH) in the US have kept pig hearts alive inside five baboons for a median of 298 days. They hope this will lead to the development of pig organs safe for transplant into humans.