Indications and Procedures (Magill’s Medical Guide, Sixth Edition)
The transplantation of organs from human donors to human recipients has been established practice in medicine since the first successful kidney transplant was performed in 1954. Its applications have been limited, however, for two major reasons. First, the demand for human-donated organs always exceeds the supply. Second, the human body naturally rejects transplants. When the immune system recognizes compounds on the surfaces of cells from any source that is “not self,” a chain reaction begins. Antibodies attack foreign proteins and mark them for destruction by white blood cells. Enzymes attack the walls of blood vessels in a transplanted organ, destroying it within hours. To prevent rejection, transplant recipients must take immunosuppressive drugs for months or years. Blocking their immune response, however, makes transplant patients susceptible to infections, some of which can be deadly.
Xenotransplantation—the transfer of cells, tissues, or organs from nonhuman animal donors to human recipients for therapeutic purposes—might solve both of these problems. A large supply of organs can, in theory, be farmed in animals such as pigs. Also, theoretically, organs can be tailor-made to prevent rejection. Genetic engineering techniques should be able to replace animal proteins and sugars on the surfaces of cells with human ones, thus creating an organ that the recipient’s immune system is tricked into...
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Uses and Complications (Magill’s Medical Guide, Sixth Edition)
One concern about xenotransplantation is that new diseases might be introduced into humans from other animals. All animals carry endogenous viruses that are part of their genetic makeup. Endogenous viruses are harmless in their natural hosts, but they can prove deadly when they cross from one species to another. For example, the Hong Kong flu virus lay harmlessly in waterbirds for many years. It then struck chickens and caused massive deaths on poultry farms, and now it infects and sometimes kills people. How the virus migrated to humans remains unknown. Also, diseases can be minor in some animals but major in humans. The herpesvirus B is one example. It gives monkeys mild cold sores but causes fatal encephalitis in people. The concern is that a virus imported into the human population through xenotransplantation might subsequently spread through other means, such as blood, air, water, or food.
Issues of morality, ethics, and religion also arise. Although the genetic makeup of other primates most closely matches that of humans, many people believe that using apes and monkeys as organ donors would be morally unacceptable. One answer to such objections is to use animals that are routinely raised and slaughtered for food. Pigs are easy to breed and care for, and they produce large litters. Their size and weight are similar to humans. Few people object to killing pigs. Much xenotransplantation research involves the...
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Perspective and Prospects (Magill’s Medical Guide, Sixth Edition)
Xenotransplantation is not a new idea. In 1906, with no knowledge of the immune system, French surgeon Mathieu Jaboulay transplanted a kidney from a pig and a liver from a goat to human patients, both of whom died. In 1964, Thomas Starzl at the University of Pittsburgh transplanted baboon kidneys into two humans. Both patients died from infections accompanied by kidney failure. That same year, a chimpanzee-to-human transplant fared a little better. The patient lived for nine months before the kidney failed.
In 1984, a child the press called “Baby Fae” was born prematurely with a severely malformed heart. She could not live long without a transplant. No human heart small enough was available, so surgeons at Loma Linda University in California gave Baby Fae the heart of a baboon. The operation went well, but Fae died of organ rejection and infection after the surgery.
In 1992, two liver transplants from baboons were attempted. The livers functioned well, but the patients died from infections. That same year, two women received livers from pigs. The transplants were not meant to be permanent but were intended as “bridges” until human donors could be found. In both women, the livers functioned well, but one woman died before a human organ could be located.
In 1995, British scientists succeeded in transplanting pig hearts into monkeys. Half the monkeys survived for forty days, but long-term survival...
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For Further Information: (Magill’s Medical Guide, Sixth Edition)
Brynie, Faith Hickman. 101 Questions About Your Immune System You Felt Defenseless to Answer…Until Now. Brookfield, Conn.: Twenty-first Century Books, 2000.
Cooper, David K. C., and Robert P. Lanza. Xeno: The Promise of Transplanting Animal Organs into Humans. New York: Oxford University Press, 2003.
Munson, Ronald. Raising the Dead: Organ Transplants, Ethics, and Society. New York: Oxford University Press, 2004.
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Xenotransplantation (Encyclopedia of Science and Religion)
Xenotransplantation is transplanting an organ or tissue from one species to another. A shortage of human body parts available for allotransplantation (transplantation to other humans) has increased interest in this alternative. Since the 1960s, attempts at xenotransplantation have been made using chimpanzee kidneys, baboon hearts and livers, and pig hearts and livers. Present efforts focus on pigs rather than primates, as pigs reach maturity and reproduce quicker than primates, and pigs are not an endangered species. While pig heart valves are used successfully to repair human hearts, xenotransplantation remains in limited clinical trials. The genetic modification of animals has the potential for reducing human rejection and the danger of transmitting dangerous pathogenic agents. Some researchers have suggested that the transplantation of pig organs to humans may be possible within five years.
How religions evaluate the morality of xenotransplantation hinges on views of animals in the created order. For example, Christianity, particularly Roman Catholicism, believes that xenotransplantation can be justified in certain circumstances since humans have a higher dignity than the animals that serve them. Moral limits, however, preclude transplantation of the encephalon and gonads that are linked indissolubly by their function with the personal identity of humans.
See also ANIMAL RIGHTS; BIOTECHNOLOGY; CHRISTIANITY, ROMAN CATHOLIC, ISSUES IN SCIENCE AND RELIGION; CLONING
Clark, M. A. "This Little Piggy Went to Market: The Xenotransplantation and Xenozoonose Debate." Journal of Law, Medicine, and Ethics 27 (1999): 13752.
Cooper, David K. C., and Lanza, Robert P. Xeno: ThePromise of Transplanting Animal Organs into Humans. New York: Oxford University Press, 2000.
Hanson, M. J. "The Seductive Sirens of Medical Transplantation: The Case of Xenotransplantation." Hastings Center Report 25 (1995): 5.
International Xenotransplantation Society. Available from .
McCarthy, Charles R. "A New Look at Animal-to-HumanOrgan Transplantation." Kennedy Institute of Ethics Journal 6, no. 2 (1996): 18388.
Pontifical Academy for Life. "Prospects for Xenotransplantation: Scientific Aspects and Ethical Considerations." September 26, 2001. Available from http://www.vatican.va/roman_curia/pontifical_academies/acdl... .
WHO Electronic Discussion Group (EDG) on InternationalXenotranplantation Policy Considerations. Available from http://www.who.int/emc/diseases/zoo/meetings/xenodg.html.
DONNA M. MCKENZIE