Xenotransplantation - Nuffield Council on Bioethics

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Animal-to-Human Transplants : the ethics of xenotransplantation Gene A gene is a length of DNA that contains the information needed to make one protein. For example, the haemoglobin gene contains the information needed to make the haemoglobin protein found in red blood cells. The DAF gene contains the information needed to make the complement regulating protein DAF (paragraph 3.25). Genetic material Genetic material refers to the material made of DNA in each cell of any organism. The DNA is divided into genes. Each gene contains the information required to produce one protein needed by the cell. Genetic modification The process of changing the genetic material of an animal or other organism. The main method of genetically modifying organisms is by transgenesis (paragraphs 3.26 - 3.28 and 4.45 - 49). Genome The term genome describes the genetic material of an organism in its entirety, containing a complete set of the information in the DNA. Heterozygote Each cell of an organism contains two copies of each gene. In a heterozygote, the two copies are different (paragraph 3.27). Compare homozygote. Higher primates Higher primates (more correctly, the simian primates) include all primate species except species such as the loris, bushbaby, ringtail lemur and aye-aye which are known as lower primates (or, more correctly, the prosimian primates) (Figure 4.1). HIV (see AIDS) Homozygote Each cell of an organism contains two copies of each gene. In a homozygote, the two copies are the same (paragraph 3.27). Compare heterozygote. Hyperacute rejection Hyperacute rejection is the rapid and strong immune response to a transplanted organ from animals, such as pigs, that are only distantly related to human beings. Within minutes the xenograft is reduced to a black, swollen mass. This is because antibodies attack the pig antigen -gal (galactosyl -1,3-galactose). Complement is activated and the cells of the transplanted organ are attacked and destroyed (paragraphs 3.24 and 3.30). Immunosuppression This refers to the inhibition of the immune response in order to prevent organ rejection. It is achieved by the use of immunosuppressive drugs which work in a variety of ways (paragraph 3.17). 138
Annex E : Glossary Islet cells (see pancreatic islet cells) Live donation This is when a living person donates an organ or tissue. The most familiar example is blood donation. Kidney donation and bone marrow donation are less common. A very new development is the donation of lung lobes or small bowel. Very occasionally live heart donation can occur, in ‘domino’ operations, in which a person receiving a heart/lung transplant donates his or her heart for transplantation into someone else (paragraphs 1.7 and 2.6). Matrix A matrix is an artificial framework used to support the living cells of a bioengineered organ or tissue. An example is the matrix that is used to support skin cells in order to produce artificial skin (paragraphs 2.30 - 2.31). MCP MCP (membrane co-factor protein) is a human complement regulating molecule present on the body’s cells. It prevents complement proteins attacking the body’s cells (paragraphs 3.13 and 3.25). Mechanical organs (see artificial organs) Molecule Molecules are small particles consisting of groups of atoms. Examples of important biological molecules are proteins and DNA (paragraphs 1.14 and 3.8). Mutation A process during which the DNA of an organism changes or mutates. In humans, this can lead to conditions such as cystic fibrosis in which a mutation has occurred in a gene required for proper lung function. The mutant gene is passed down from parent to offspring and so the condition is inherited. In viruses, and other infectious organisms, mutations can lead to the emergence of organisms with new characteristics. In some case they may be more infectious, or cause more serious disease (paragraph 6.9). Organ An organ is a structure formed of different types of tissue that performs a particular function. Examples are the kidney, heart, lungs and liver. Organism Any living thing, for example, an animal, plant, fungus, bacterium. Viruses and prions are not normally considered to be organisms since they do not show all the characteristics of living things. But, for convenience, in this report, the term organisms was taken to include viruses and prions (paragraph 6.2). Organ rejection This refers to the destruction of a transplanted organ due to the immune response of the recipient. The transplanted organ is seen as foreign by the body and so it is attacked by the antibodies and T-cells of the immune system (paragraphs 3.9 - 3.14). 139
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NUFFIELD COUNCIL ON BIOETHICS Anima
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Preface Preface Since the N
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Table of contents Table of contents
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Working Party on Xenografts Working
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Summary of recommendations Summary
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Summary of recommendations Effects
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The promise and the problems Chapte
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Alternatives to xenotransplantation
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Xenotransplantation</strong
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Animal concerns : principles Chapte
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Animal concerns : practice genetic
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Transmission of infectious diseases
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Early patients Chapter 7 Early pati
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Early patients to clinical trials.
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Xenotransplantation - Nuffield Council on Bioethics

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