Glossary Of Transplant Terms

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Acute rejection: Occurs within days or months following transplantation. It is mainly caused by the action of T-cells acting against graft antigens, leading to rejection.
Allele: Any alternative form of a gene containing specific inheritable characteristics that occupy corresponding positions (loci) on paired chromosomes.
Allograft: Graft of organ or tissue between two individuals of the same species.
Allotransplantation: The transplant of organs or tissues between genetically different members of the same species.
Antibody: A serum protein consisting of soluble molecules that are part of the body's immune system; they are produced in response to and bind to substances, usually foreign, known as antigens.
Antigen: A substance molecule recognized as foreign by the immune system and which may stimulate the production of a specific antibody and/or stimulate T-cells.
Anti-microbial: An agent which kills or inhibits the growth of micro-organisms.
Autoantibody: An antibody that reacts with antigens on a person's own cells and tissues.
Autograft / autologous: Graft of organ or tissue from the same individual. Related to "self" antigen.

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Autoimmune disease: Disease in which the immune system mistakenly attacks the body's own cells and tissues; this immune reaction is the basis of a variety of e.g. diabetes, rheumatoid arthritis and system lupus erythematosus, among others.
B-cells (B-lymphocytes): A class of white blood cells of the immune system that interact to produce antibodies and the 'antibody mediated' immune response.
Bone marrow: Bone marrow is the source of all blood cells, and it is present in the cavities of bones.
Brain Death: Occurs when a person has irreversibly lost the capacity for consciousness combined with the irreversible loss of the capacity to breathe. It represents the point at which a person is accepted as being dead even though their heart is still beating. Diagnosis of Brain Death is determined from detailed criteria.

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Cadaveric Organs: Organs for transplantation obtained from individuals who have died.
Cardiomyopathy: Any disease of the heart muscle that causes a reduction in the force of heart contractions and a resultant decrease in the efficiency of circulation of blood.
Cell: The smallest component of life, capable of carrying out essential life processes.
Chimerism: (of tissue/organ) A state in which two or more genetically different populations of cells co-exist.
Chronic rejection: Usually occurs many months or years after transplantation, and leads to scarring and loss of function in the transplanted organ.
Ciclosporin / cyclosporin: Selective immunosuppressant, developed by Sandoz and marketed as Sandimmun, which in the early 1980's improved and increased the survival of both transplant recipients and their grafts.
Cirrhosis: A diseased condition in which healthy liver tissue becomes replaced by fibrous tissue similar to a scar.
Corticosteroids: Any of a number of hormonal steroids substances obtained from the cortex of the adrenal gland (but excluding sex hormones of adrenal origin). Used clinically for hormonal replacement therapy, as antineoplastic, anti-allergic and anti-inflammatory agents, and to suppress the immune response.
Cytostatic: Preventing cell growth and proliferation.
Cytotoxic: Chemicals that destroy cells or prevent their multiplication.

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Dialysis: The process of blood detoxification (haemodialysis, peritoneal dialysis), a treatment which is used for patients with end stage renal failure.
DNA (deoxyribonucleic acid): The chemical substance which encodes the genetic information required to determine the structure and function of an organism.
Domino donation: Occurs when a patient receives a multi-organ transplant and his/her healthy organ is donated to another patient; for example a patient receives a heart/lung transplant and donates his/her heart to another patient.

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Endothelial cells/Endothelium: Endothelial cells from the lining of blood vessels, the endothelium.
End-stage organ disease: A disease that leads, ultimately, to functional failure of an organ. Some examples are: emphysema (lungs), cardiomyopathy (heart) and polycystic kidney disease (kidneys).
Ex vivo support: A method of partially taking over the function of a failing organ by passing the patient's blood through a substitute organ placed outside the body (extra corporeal support).

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Gene: A functional unit of genetic material (DNA). One gene may have different forms (allelles).
Gene therapy: Treatment of genetic diseases by providing the correct or normal form of the abnormal gene causing a disease.
Genetic disease: A disease due to an abnormal condition of one or more genes. While most diseases have some genetic component, the term genetic disease is usually applied to those cases where one or two genes determine the disease, such as sickle cell anemia and cystic fibrosis.
Genetic manipulation: The process by which the DNA of an organism is changed by artificial means.
Genome: A term used to describe the genetic material of a particular organism in its entirety.
Graft: Transplanted organs, tissues or cells.
Graft failure: Absence of adequate function in a transplanted organ or tissue.
Graft survival rates: The percentage of patients who have functioning grafts; graft survival rates are usually given for chronological landmarks (e.g., 1 year, 2 years).

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Hepatitis virus: A virus causing inflammation of the liver. There are several different types of hepatitis-causing viruses.
Heterotopic site: A graft transplanted to an unnatural site in the body (e.g., kidneys joined to the iliac vessels).
Heterozygous: An individual carrying one copy of a gene in each cell.
Histocompatibility testing: Determining how closely the HLA-antigens of the donor and the recipient are matched and the likelihood that the recipient will reject the donor tissue.
HLA (Human Leucocyte Antigens): The transplantation antigens (i.e., the antigens that are the major targets of rejection) of humans. HLA characteristics determine immunity - the ability to recognize foreign or "non-self" antigens. The wider the differences in the HLA characteristics of donor and recipient, the greater the chance of organ rejection.
Homozygous: An individual carrying two copies of a gene in each cell.

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Immune response: A selective response mounted by the immune system of humans and animals in which specific antibodies and/or T-cells are produced as a defence against invading micro-organisms, transplanted tissue and other material recognized as foreign. There are two main types of immune response: the 'antibody-mediated (or humoral)' response, and the 'cellular' response (mediated by T-cells).
Immune System: Collectively the cells and tissues which enable humans and animals to mount a specific protective response to invading micro-organisms, transplanted tissues and other material recognized as foreign by the body.
Immunity: A state of resistance to the onset of disease caused by a specific infectious agent. Immunity may be conferred: by innate non-specific body defenses such as the skin and mucosal surfaces; or through immunological 'memory' of a specific immune response which was mounted against the same (or similar) infectious agent during a previous exposure.
Immunocompetent: Capable of developing an immune response.
Immunocyte: Any immunologically competent cell.
Immunodeficiency: Decreased or compromised immune response to antigens with the appropriate cellular immunity reaction.
Immunogenicity: The ability to mount an immune response.
Immunoglobulins: Glycoproteins which function as antibodies. These include different classes based on structural and antigenic differences such as IgA, IgD, IgE, IgG and IgM. All antibodies are immunoglobulins but it is not certain that all immunoglobulins have antibody function.
Immunological disease: A disease due to a dysfunction of the immune system.These are autoimmune, allergic and immunodeficiency diseases.
Immunosuppression: Therapy, usually pharmaceutical, to reduce the magnitude of the immune response. Immunosuppression is the treatment for graft rejection and autoimmune disease. - Corticosteroids - Azothioprine - Ciclosporine - MMF/RS61443 - Tacrolimus/FK506 - Cyclofosfamide
Inflammation: The succession of changes that occur in living tissue when it is injured. The inflamed area undergoes continuous change as the body repair processes start to heal and replace injured tissue. Inflammation may also occur as a result of an inappropriate immune response (e.g., in autoimmune disorders).
Islet cells: (see Pancreatic Islet Cells of Langerhans).
Isograft: Graft of organ or tissue between two, genetically - and antigenically-identical individuals.

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Keratinocytes: A type of skin cells.

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Leucocytes: White blood cells.
Loci: Position of a gene on a chromosome.
Lymph: A body fluid that circulate within the lymphatic system.
Lymphatic System: A network of vessels that conveys salts, water, proteins etc. constituting lymph from the tissue fluids to the bloodstream.
Lymphocytes: Group of white blood cells, being cells of the immune system.

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Macrophage: Large blood cells that engulf bacteria, fungi and debris of inflammation in the body tissues.
Major histocompatibility complex (MHC): Group of genes that code for proteins involved in transplantation rejection and the regulation of the immune response. In man they are located on chromosome 6.
Micro-organism: Microscopic organisms, including bacteria, viruses and fungi. Some are capable of causing disease in humans and animals.

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Organ: A collection of different tissues that form a distinct structural and functional entity in the body e.g. liver, heart, brain and kidney.
Organ exchange organizations: National and international organizations responsible for the distribution of donor organs and tissues, registration and tracking of recipients and recording data related to transplant outcomes. The first international non-profit making organ exchange organization is Eurotransplant (Austria, Belgium, Germany, Luxemburg, and the Netherlands). The central office is in Leiden, the Netherlands.
Organism: An individual living thing (animal, plant or micro-organism).
Orthotopic site: A graft placed in its normal position (e.g., a kidney joined to renal vessels).

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Pancreatic Islet Cells of Langerhans: Groups of cells scattered throughout the pancreas which secrete glucagon and insulin (hormones involved in regulating blood sugar levels).
Pathogen: An infectious agent that has the capacity to cause disease.
Pathognomonic: Specifically distinctive or characteristic of a disease.
Phagocytose: To engulf and kill bacteria or engulf and digest debris of inflammation. (see macrophage).
Plasma: Fluid in which blood cells are bathed.
Presumed consent policy: Tissues and organs can be taken unless the donor has objected during lifetime against organ/tissue donation. Belgium, France, Denmark, Sweden, Austria, Switzerland and Israel have adopted presumed consent policies of which the application may differ from country to country.

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Rejection (graft): The immunological response to the transplanted tissues or organs; if rejection is not controlled, it will eventually lead to graft failure or graft-versus-host disease (see also transplant rejection).
Retrovirus: A family of viruses with a special replication mechanism which includes incorporation of its genetic material into the DNA of the organism it has infected. Examples of retroviruses include the Human Immunodeficiency Virus (HIV) and certain oncogenic viruses.

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Septicaemia: Presence of bacteria or other micro-organisms in the bloodstream. A potentially fatal condition.
Serum: The fluid component of clotted blood that contains antibodies and other soluble material.
Species: A group of organisms that have similar characteristics and can interbreed to produce fertile offspring.

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T-cell (=T lymphocyte): A class of white blood cells of the immune system that interact to produce the 'cellular' immune response. Mature T-cells can be divided into two major subsets, "CD4+" and "CD8+" that differ in function. 'Killer' T-cells (a subset of "CD8+") directly attack and kill cells bearing foreign antigens (See T-lymphocytes).
Thrombosis: Formation of blood clots in veins and arteries.
Tiss;ue: An organized aggregate of similar cells that perform a particular function, for example bone marrow, nerve tissue.
Tolerance: A state of immunological non-responsiveness to one or more antigens. Donor specific tolerance means tolerance of the donor's antigens by a transplant recipient.
Transgenic organism: This describes an organism which, through genetic modification, has a heritable foreign gene (known as a transgene). e.g. transgene pig.
Transplant rejection: The process where the host immune response recognizes the transplanted tissue as foreign and acts against it leading to damage/destruction of the tissue. Various forms of rejection have been defined with respect to time to rejection and the elements of the immune response which are involved (see Hyperacute, Acute vascular, Acute cellular and Chronic rejection).
Transplantation: The removal (procurement) and implantation of organs, tissues or cells from one organism into another.
Transplantation, allogeneic (allograft): Transplantation between genetically different members of the same species. Nearly all organ and bone marrow transplants are allografts. These may be between brothers and sisters, parents and children or between donors and recipients who are not related to each other.
Transplantation, autologous: Transplantation of an organism's own cells or tissues; autologous transplantation may be used to repair or replace damaged tissue. Autologous bone marrow transplantation permits the usage of more severe and toxic cancer therapies by replacing bone marrow damaged by the treatment with marrow that was removed and stored prior to treatment.
Transplantation, syngeneic: Transplantation between genetically identical members of the same species (e.g., identical twins).
Transplantation, xenogeneic (xenograft): Transplantation between members of different species; for example, the transplantation of animal organs into humans.

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Uraemia: The clinical state which may arise as a result of kidney failure.
Uveitis: An autoimmune disease, characterized by inflammation of the pigmented layer of the eye.

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Vascular: Appertaining to blood vessels (arteries, capillaries and veins) and/or lymph vessels.
Vasculitis: Inflammation of a blood or lymph vessel.
Vertical transmißion: The transmission of infection directly from parent to offspring. This can take place in utero via egg, sperm, placenta, or post-natally via milk, blood or contact, etc.
Viable: Capable of living (through continued metabolism); this will apply to organs and most tissues which may be transplanted. this does not include sterilized bone, which is 'non-viable'.
Virus(es): Minute micro-organisms, some of which can reside and replicate in human and animal cells. Some viruses cause disease.

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White blood cells: Blood cells which are involved in protecting the body against foreign substances and which constitute part of the immune system.

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Xenoantigen: Antigens of transplants from discordant species.
Xenoreactive natural antibodies (XNA): Pre-existing natural antibodies that bind to xenoantigens on the surface of the cells of a xenotransplant
Xenotransplantation: The transplantation of tissue and organs between species e.g. pig kidney to human recipient.
Xenozoonosis: A zoonotic infection which can be transmitted by the xeno-transplantation of animal tissues or organs.