On Dec. 12, 2004, the first successful cow-to-monkey kidney transplant was performed at Dokkyo Medical School, Tochigi, in Japan. The recipient monkey survived for one day with no sign of rejection.
Rejection has always been an issue in transplantation. When tissues, cells or organs are introduced to another species, they are recognized by the recipient’s body as being foreign and attacked by the immune system. In xenotransplantation, the distant evolutionary relationship between any two species can lead to hyperacute rejection.
To reduce the risk of rejection, a genetically modified source animal was used in this experimental transplant. They had produced a “aGal-knokout” genetically modified cow clone without aGal antigen which would trigger an immunological response in monkies and humans.
The cloned cow was born in December and did not survive for long. Kidneys were taken out after it died and were transplanted to the monkey. After the operation, the monkey showed no sign of hyperacute rejection and was able to urinate, which proved that kidneys functioned normally. The recipient monkey died the next day, of causes unrelated to rejection.