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Titlesort descending Definition
Acquired Immunodeficiency Syndrome (AIDS) An acquired defect or cellular immunity associated with infection by the human immunodeficiency virus (HIV). AIDS increases susceptibility to opportunistic infections. The CDC lists numerous infections and cancers that, in the presence of HIV infection, constitute an AIDS diagnosis.
Acute Describing a medical condition which is marked by rapid onset, severe symptoms, and short course.
Acute Intermittent Porphyria A rare autosomal dominant metabolic disorder characterized by a deficiency of the enzyme porphyobilinogen deaminase, which affects the production of the oxygen-binding prosthetic group of hemoglobin. Major symptoms include abdominal pain or cramping and neuropathies, sometimes leading to misdiagnosis as a psychiatric disorder.
Agammaglobulinemia A nearly total absence of immunoglobulins resulting in the loss of ability to produce immune antibodies.
Agglutination The clumping together of red blood cells or bacteria; a type of antigen-antibody reaction in which a solid antigen clumps together with a soluble antibody. This physiological property is useful in laboratory testing.
AHF See: Anti-Hemophilic Factor
AIDS See: Acquired Immunodeficiency Syndrome
Albumin One of a group of simple proteins made by the liver. Serum albumin is the main protein found in the blood (about 60 percent of the total). It is responsible for much of the plasma colloidal osmotic pressure and serves as a transport protein. Human albumin USP is administered intravenously to restore blood volume following shock, trauma, surgery, and burns.
Anaphylaxis An unusually severe allergic reaction, usually to food, drug, or insect bite. It occurs between an allergic antigen, and IgE bound to mast cells, stimulating the sudden release of immunological mediators locally and throughout the body. Initial symptoms appear within minutes, but recurrence may follow hours later. Hypersensitivity must have been induced in the individual in a prior exposure to the allergen for an anaphylactic reaction to occur. It is the initial exposure that results in the IgE binding to mast cells. The reaction can result in cardiovascular shock and death. It is categorized as local or systemic. Local anaphylactic reactions include hay fever, hives, and allergic gastroenteritis. Systemic anaphylaxis, which produces peripheral vasodilation, brochospasm, and laryngeal edema, can be life threatening.
Anti-Hemophilic Factor (AHF) Blood coagulation Factor VIII, a protein substance in blood plasma that is essential in the blood clotting process. Hemophilia A, the most common form of blood clotting disorder, is caused by a deficiency of AHF. AHF can be separated out of human plasma and given to hemophiliacs to temporarily correct the bleeding tendency.
Antibody An immune, or protective, protein secreted into the blood in response to foreign substances, called antigens, being introduced to the body. It combats these viruses, bacteria, and parasites, and some transplanted organs, by binding to the foreign substance. Once bound, the antibody leads to the neutralization or destruction of the antigen, providing protection from most common infections. Antibodies neutralize or destroy antigens in several ways. They can directly lyse the antigen, neutralize toxins released by bacteria, opsonize the antigen (form a complex to stimulate phagocytosis), promote antigen clumping (agglutination), or prevent the antigen from adhering to host cells. Antibodies are Y-shaped immunoglobulins produced by B- lymphocytes. Their synthesis is induced by specific antigens. They combine with the specific antigens which stimulated their production, and not with unrelated antigens. Antibodies are responsible for humoral immunity. Inhibitors that occur in response to replacement therapies for Hemophilia A are antibodies to Factor VIII.
Antigen In broad usage, any substance or entity which the body recognizes as foreign and induces the production of antibodies to neutralize or destroy the antigen. Antigens include toxins, bacteria, foreign blood cells, and the cells of transplanted organs. More specifically, the antigen is the protein marker on the surface of a cell that marks it as "self" or "non-self." The antigen identifies the type of cell (skin, kidney, foreign substance). Autoantigens are markers on the body's own cells; markers on all other antigens are called foreign antigens.
Antigen-Antibody Reaction The binding of a specific antigen with its corresponding antibody. It may result in agglutination, precipitation, or increased susceptibility to phagocytosis.
Antigen-Specificity The property B- and T-lymphocytes gain through an initial exposure to an antigen to recognize that specific antigen if it again enters the body. Antigen-specificity allows the body to more quickly mediate an immune response to each subsequent exposure to that specific antigen. This property is the basis of immunization.
Antithrombin III A small protein molecule which inactivates several enzymes in the coagulation cascade.
Antithrombin III Deficiency A rare hereditary disorder, often presenting as frequent venous thrombosis or pulmonary embolism. Patients are treated with anticoagulants and antithrombin concentrates.
Autoimmune Disease A disease occurring when an individual's immune system attacks the body's own tissues or extracellular proteins. This disease results from a reduction in the body's tolerance to the antigens located on its own cells. For example, multiple sclerosis results from the body's own antibodies attacking the myelin sheath that covers nerve cells. Researchers have begun clinical studies using IVIG to treat certain autoimmune diseases.