Xenotransplantation: Animal Rights and Human Wrongs
Mani, Vasudevan, Mathew, Ryan, Ethics & Medicine
The first successful human-to-human organ transplant was performed in 1954 when a kidney was transferred between two identical twins. In the years since this groundbreaking operation improvements in transplant surgery and an increasing ability to control organ rejection using imunosupressive medication has made transplantation the treatment of choice for a new generation. Unfortunately, these advancements have resulted in transplantation becoming a victim of its own success, as waiting lists have increased along with the waiting time for donor organs. For these reasons the use of animal organs for human transplantation is seriously being considered. Two groups of animals have been considered as donors: non-human primates and large non-primates such as pigs.1
Whilst many researchers in this field are very optimistic about the future, many opponents are concerned about the effects on public health and the environment. The primary barrier to transplantation is immunological rejection. With xenotransplantation an additional mechanism of rejection called hyperacute rejection occurs. Immunosuppressive drugs cannot control hyperacute rejection. For this reason, the majority of xenotransplantation trials attempted to date in humans have used chimpanzee or baboon organs. However the problem will occur with xenotransplantation into humans of organs from more distantly related species such as pigs.
This article highlights the ethical issues associated with the use of animal organs, and the impact of xenotransnlantation on animal communities.
The use of animal cells and tissues in the treatment of man is not a new innovation. In the early 17th century attempts were made to resuscitate humans by transfusing them with animal blood. In 1682, the skull of a Russian nobleman who had been injured in battle was reportedly repaired using a piece of canine bone. Later, in the 19th century, surgeons attempted on many occasions to transplant tissue from animals into humans, primarily skin grafts from dogs, cats, rabbits, rats, pigs, chickens, cockerels, pigeons, and, most commonly, from frogs. Surprisingly, even sections of apes' testicles were grafted on to men in the early 20th century in an attempt to reverse their impotence. The transplantation of kidneys, livers, and hearts from animals into humans were recorded as early as 1905, although the results have been dissapointing.2
The Problem of Rejection
Xenotransplantation is currently at the research stage. If it is to develop into a successful clinical procedure it will involve the breeding and killing of animals on a large scale in order to provide organs and tissue for transplantation.3 The focus of these experiments is centred on both non-human primates and pigs. The primary barrier to transplantation is immunological rejection. With xenotransplantation an additional mechanism of rejection called hyperacute rejection can occur, when the recipient's blood already contains antibodies to the foreign tissue. Binding of these antibodies to the graft activates a set of human serum-proteins, called complement. This results in breakdown of the blood vessels in the graft and coagulation of the patient's blood throughout the transplanted organ, which then dies within minutes. Immunosuppressive drugs cannot control Hyperacute rejection. For this reason, the majority of xenotransplantation trials attempted to date in humans have used chimpanzee or baboon organs.4 There are advantages in using pigs as a source of xenografts. Pigs are available in large numbers and can be bred easily and rapidly. Knowledge has improved in the area genetic engineering in pigs, so this may help to overcome the existing immunological barriers. Furthermore, they are physiologically similar to humans in cardiovascular and pulmonary function, renal anatomy and excretion, digestion, and susceptibility to disease.5
The Balance of Animal Suffering and Human Benefit
Many people world wide believe that although it is imperative to maintain the protection and integrity of the animal population, in certain circumstances human life does outweigh that of an animal. …