Xenotransplantation is the procedure entails live organs, tissues and cells being transplanted into a human recipient from other organisms. Xenotransplantation was first attempted by doctors over a century ago, but all of these attempts failed due to immune responses, which were not known to scientists until many years later. The organs that the scientists attempted to transplant into humans include “pigs, goats, lambs, or monkeys”. Due to the many failures, the xenotransplantation research greatly slowed, but in 1944 a scientist named Peter Medawar, discovered that if the organism which is receiving the transplant recognizes that the new organ is foreign it will cause the organ to be attacked by the immune system and subsequently reject.
