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Glossary Acquired immune deficiency syndrome (AlDS). A severe manifestation of infection with human immunodeficiency virus (HIV). Active surveillance. The process of actively seeking out and identifying health problems within a population. (See also Passive surveillance.) AlDS-related complex (ARC). A variety of chronic symptoms and phys- ical findings that occur in some persons who are infected with HIV but do not meet the Centers for Disease Control's definition of AIDS. Symptoms may include chronic swollen glands, recurrent fevers, unintentional weight loss, chronic diarrhea, lethargy, minor alterations of the immune system (less severe than those that occur in AIDS), and oral thrush. ARC may or may not develop into AIDS. Antibody. A protein in the blood produced in response to exposure to specific foreign molecules. Antibodies neutralize toxins and interact with other components of the immune system to eliminate infectious microorganisms from the body. Antigen. A substance that stimulates the production of antibodies. ARV (AIDS-associated retrovirusJ. Name given by researchers at the University of California at San Francisco to isolates of the retrovirus that causes AIDS. Autologous transfusion. A blood transfusion in which the patient re- ceives his or her own blood, donated several weeks before elective surgery. 353
354 GLOSSAR Y B Iymphocyte (or B cell). A type of white blood cell that produces antibody in response to stimulation by an antigen. Candida albicans. A yeastlike fungus that causes whitish sores in the mouth. The infection is called candidiasis or, more commonly, thrush. In AIDS patients, candidiasis often extends into the esophagus. Case-control study. A design for epidemiologic studies that matches individuals with a disease or health problem (cases) with others who do not have that condition (controls). Frequently, individuals included in the study are matched for factors such as age, race, socioeconomic status, occupation, and area of residence. Comparisons are then made between the two groups. Casual contact. Refers to day-to-day interactions between HIV-infected individuals and others in the home, at school, or in the workplace. It does not include intimate contact, such as sexual or drug use interac- tions, and it implies closer contact than chance passing on a street or sharing a subway car. CD4 Iymphocyte or CD4 T cell. A T lymphocyte that expresses the cell surface marker molecule CD4. The majority of these cells are thought to consist of helper/inducer lymphocytes, which play important regu- latory roles in the human immune system. These cells appear to be the primary targets for infection by HIV. CD8 Iymphocyte or CD8 T cell. A T lymphocyte that expresses the cell surface marker molecule CD8. The majority of these cells are thought to consist of suppressor/cytotoxic lymphocytes, which play important regulatory and functional roles in the human immune system. Cell-mediated immunity. A defense mechanism involving the coordinated activity of two subpopulations of T lymphocytes, helper T cells and killer T cells. Helper T cells produce a variety of substances that stimulate and regulate other participants in the immune response. Killer T lymphocytes destroy cells in the body that bear foreign antigens (e.g., cells that are infected with viruses or other microorganisms). Cofactor. A factor other than the basic causative agent of a disease that increases the likelihood of developing that disease. Cofactors may include the presence of other microorganisms or psychosocial factors, such as stress. Cryptosporidium. A protozoan parasite that causes severe, protracted diarrhea. In persons with a normal immune system, the diarrhea is self-limited and lasts one to two weeks. In AIDS patients, the diarrhea often becomes chronic and may lead to severe malnutrition. Cytomegalovirus (CMV). A virus that belongs to the herpesvirus group.
GLOSSAR Y 355 Prior to the appearance of AIDS, it was most commonly associated with a severe congenital infection of infants and with life-threatening infections in patients who had undergone bone marrow transplants and other procedures requiring suppression of the immune system. It rarely causes disease in healthy adults. In AIDS patients, CMV may produce pneumonia, as well as inflammation of the retina, liver, kidneys, and colon. Cytopathic. Disease-induced or disease-inducing changes to cells. DNA (deoxyribonucleic acid). A nucleic acid found chiefly in the nucleus of living cells that is responsible for transmitting hereditary character- istics. ELISA. An acronym for "enzyme-linked immunosorbent assay," a test used to detect antibodies against lIIV in blood samples. Encephalitis. Inflammation of the brain. Encephalopathy. Any degenerative disease of the brain. End-stage renal disease (ESRD). A collection of diseases affecting the kidney and resulting in the failure of that organ, necessitating hemo- dialysis or transplantation to sustain life. Epstein-Barr virus. A member of the herpes group of viruses and the principal cause of infectious mononucleosis in young adults. It also has _ . .. . ~ ~ . · . 1 1 _ 1 ~ ~ ~ _ _ -1 _ ~ ~ ~ ~ been implicated as a causal factor in tne Development ol DULK15L lymphoma in Africa. False negative. A negative test result for a condition that in fact is present. False positive. present. Frank AIDS. Those cases of infection with HIV meeting the Centers for Disease Control's definition of AIDS. A positive test result for a condition that in fact is not Genome. The genetic endowment of an organism. Gold standard. In medical testing, an independent means of unequivo- cally verifying the presence or absence of the condition being tested for. Hemophilia. A rare, hereditary bleeding disorder of males, inherited through the mother, caused by a deficiency in the ability to make one or more blood-clotting proteins. Herpes simplex. An acute disease caused by herpes simplex viruses
356 GLOSSARY types 1 and 2. Groups of watery blisters, often painful, form on the skin and mucous membranes, especially the borders of the lips (cold sores) or the mucous surface of the genitals. Herpesvirus group. A group of viruses that includes the herpes simplex viruses, the varicella-zoster virus (the cause of chicken pox and shingles), cytomegalovirus, and Epstein-Barr virus. HIV (human immunodeficiency virusJ. The name proposed for the caus- ative agent of AIDS by a subcommittee of the International Committee on the Taxonomy of Viruses. (See also ARV, HTLV-III, and LAY.) HTLV-III (human T-cell Iymphotropic virus type 111~. The name given by researchers at the National Cancer Institute to isolates of the retrovirus that causes AIDS. Humoral immure. The human defense mechanism that involves the production of antibodies and associated molecules present in body fluids such as serum and lymph. Immune system. The natural system of defense mechanisms, in which specialized cells and proteins in the blood and other body fluids work together to eliminate disease-producing microorganisms and other foreign substances. lnterferons. A class of proteins important in immune function and known to inhibit certain viral infections. Interleukin-2. A substance produced by T lymphocytes that stimulates activated T lymphocytes and some activated B lymphocytes to prolif- erate. Also known as T-cell growth factor. In vitro. Literally, within glass. The term refers to those experiments conducted in tissue culture or another artificial environment. In vivo. Literally, within a living body. The term refers to those experi- ments conducted in animals or humans. Interstitial pneumonitis. Localized acute inflammation of the lung. Inter stitial pneumonitis persisting for more than two months in a child (under 13 years of age) is indicative of AIDS unless another cause is identified or tests for HIV are negative. Intravenous. Injected into or delivered through a needle in a vein. Kaposi's sarcoma. A cancer or tumor of the blood and/or lymphatic vessel walls. It usually appears as blue-violet to brownish skin blotches or bumps. Before the appearance of AIDS, it was rare in the United States and Europe, where it occurred primarily in men over age 50 or 60, usually of Mediterranean origin. AIDS-associated Kaposi's sar- coma is much more aggressive than the earlier form of the disease.
GLOSSAR Y 357 LAY (Iymphadenopathy-associated virus). The name given by French researchers to the first reported isolate of the retrovirus now known to cause AIDS. This retrovirus was recovered from a person with lymphadenopathy (enlarged lymph nodes) who also was in a group at high risk for AIDS. Lentiviruses. A subfamily of retroviruses that includes the visna viruses of sheep, the equine infectious anemia virus of horses, and the caprine arthritis-encephalitis virus of goats. Most researchers believe that HIV, the cause of AIDS, also belongs to this subfamily. The animal lenti- viruses produce diverse chronic diseases in their natural hosts, but all cause encephalitis. The diseases are characterized by erratic relapses and remissions. The visna viruses cause a chronic interstitial pneumo- nitis similar to that seen in AIDS virus infections in infants. Lentiviruses persist in the body by evading natural defense mecha- nisms; the chronic carrier state in which infected animals do not get sick themselves but can transmit the virus to other animals is com mon. Macrophage. A type of white blood cell that has the capacity to ingest or phagocytize foreign particulate matter, such as bacteria. Mitogen. A substance that induces cell division. Monocyte. A phagocytic white blood cell that engulfs and destroys bacteria and other disease-producing microorganisms. It produces interleukin-1, a substance that activates T lymphocytes in the presence of antigen. Mycobacterium avium-intracellulare. A bacterium related to the orga- nism that causes tuberculosis in humans, rarely seen by physicians prior to the appearance of AIDS. In AIDS patients it may cause a disseminated disease that responds poorly to therapy. Oncoviruses. A subfamily of retroviruses that includes tumor-causing agents such as the Rous sarcoma virus and the bovine leukemia virus. Opportunistic infection. An infection caused by a microorganism that rarely causes disease in persons with normal defense mechanisms. Parenteral. Involving introduction into the bloodstream. Passive surveillance. The process of monitoring health problems through the receipt of reports on those problems. (See also Active surveillance.) Persistent generalized Iymphadenopathy (PGL). A condition characterized by persistent, generalized swollen glands in the absence of any current illness or drug use known to cause such symptoms.
358 GLOSSAR Y Phagocyte. A cell in blood or tissues that binds to, engulfs, and destroys microorganisms, damaged cells, and foreign particles. Pneumocystis carinii pneumonia. The most common life-threatening opportunistic infection diagnosed in AIDS patients. It is caused by the parasite Pneumocystis carinii. Prospective cohort study. A design for epidemiologic studies that follows a group of similar individuals over time, noting who develops the health problem of interest and who does not and comparing these two groups at the end of the study. Provirus. A copy of the genetic information of an animal virus that is integrated into the DNA of an infected cell. Copies of the provirus are passed on to each of the infected cell's daughter cells. Retrovirus. ~ class of viruses that contain the genetic material RNA and that have the capability to copy this RNA into DNA inside an infected cell. The resulting DNA is incorporated into the genetic structure of the cell in the form of a provirus. Reverse transcriptase. An enzyme produced by retroviruses that allows them to produce a DNA copy of their RNA. This is the first step in the virus's natural cycle of reproduction. RNA (ribonucleic acid). A nucleic acid associated with the control of chemical activities inside a cell. One type of RNA transfers information from the cell's DNA to the protein-forming system of a cell outside the nucleus. Some viruses carry RNA instead of the more familiar genetic material DNA. Sensitivity. In serologic testing, the percentage of people who test positive who in fact do have the condition being tested for. (See also Specificity.) Seroconversion. The initial development of antibodies specific to a particular antigen. Serologic study. A study that compares the characteristics of the serum of individuals, especially those markers in blood that indicate exposure to a particular agent of disease. Seroposifive. In the context of HIV, the condition in which antibodies to the virus are found in the blood. Shooting galleries. Locations where drug addicts gather for the admin- istration of illicit drugs, often with sharing of injection equipment. Specificity. In serologic testing, the percentage of people who test negative who in fact do not have the condition being tested for. (See also Sensitivity.)
GLOSSAR Y 359 Subunit vaccine. A vaccine that contains only portions of a surface molecule of a disease-producing microorganism. Syndrome. A pattern of symptoms and signs, appearing one by one or simultaneously, that together characterize a particular disease or dis- order. T Iymphocyte (or T cell). A cell that matures in the thymus gland. T lymphocytes are found primarily in the blood, lymph, and lymphoid organs. Subsets of T cells have a variety of specialized functions within the immune system. T4 Iymphocyte (or T4 cell). A synonym for CD4 T cell. T8 Iymphocyte (or T8 cell). A synonym for CD8 T cell. Toxoplasma gondii. A protozoan parasite that is one of the most common causes of inflammation of the brain in AIDS patients. The infection is called toxoplasmosis. . Viremia. The presence of virus in circulating blood, which implies active viral replication. Vision. A complete virus particle. Western blot technique. A test that involves the identification of antibod- ies against specific protein molecules. This test is believed to be more specific than the ELISA test in detecting antibodies to HIV in blood samples; it is also more difficult to perform and considerably more expensive. Western blot analysis is used by some laboratories as a confirmatory test on samples found to be repeatedly reactive on ELISA tests.