Why are transplanted organs rejected?
Nearly all transplanted organs trigger some rejection problems in their new owner, even when they are from the same species. That’s why transplant patients take anti-rejection drugs. Only transplants between identical twins are completely accepted. Rejection occurs because the recipient’s immune system recognises that the new organ is not its own. It’s foreign. If the organ comes from a different species it is rejected within a few minutes in a process called hyperacute rejection. Pre-programmed antibodies in the recipient’s bloodstream target the xenoantigens – the flags which say ‘I am pig’ – all over the transplanted organ and trigger a destructive chain reaction. The blood supply to the transplanted organ is blocked, cells die, and the organ stops working.
