Glossary of HIV/AIDS Terms
This glossary contains 1,600 terms and is maintained by the editors of the San Francisco AIDS Foundation's Bulletin of Experimental Treatments for AIDS.
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B cell (aka B lymphocyte): an immune system white blood cell that mediates the humoral (Th2) immune response; B cells are produced in the bone marrow and mature into plasma cells, which produce antibodies. Compare with T cell.
back-mutation: the reversion of a mutant strain of a microorganism back to its natural, wild-type state.
bacteremia: the presence of bacteria in the blood.
bacteria (singular bacterium): simple single-celled microorganisms, many of which can cause disease; bacteria are classified by their shape (e.g., rod, spirochete), staining properties (Gram positive or Gram negative), and habitat (aerobic, anaerobic).
bacterial vaginosis: a condition caused by the overgrowth of anaerobic bacteria (e.g., Gardnerella vaginalis) in the vagina, resulting in irritation and discharge.
Bactrim: brand name of trimethoprim-sulfamethoxazole (TMP-SMX).
basal metabolic rate: the body's resting level of energy expenditure; the number of calories needed to sustain basic life processes during a 24-hour period.
baseline: an initial or known value (e.g., CD4 cell count, HIV viral load) against which later measurements can be compared.
basophil: a type of white blood cell that releases chemicals that mediate allergic reactions and influence the activity of other immune cells.
bDNA: See branched-chain DNA (bDNA) assay.
Beck Depression Index: a written self-report questionnaire used to measure clinical depression.
benign: refers to a mild, nonlethal illness, especially a noncancerous neoplasm. Contrast with malignant.
beta carotene: a reddish-orange antioxidant pigment found in dark yellow or orange fruits and vegetables; a precursor of vitamin A that is stored in the liver and converted as needed.
beta cell: an insulin-producing cell located in the Islets of Langerhans in the pancreas.
Bethesda System: a system for staging abnormal intraepithelial cell changes (neoplasia); categories include atypical squamous and glandular cells of undetermined significance (ASCUS and AGCUS), high-grade and low-grade squamous intraepithelial lesions (SIL), and carcinoma (cancer).
bias: in a clinical trial, a false association or conclusion that results from the failure to account for skewing or influencing factors (e.g., subjects' knowing which study treatment they are taking).
bid: twice daily.
biguanides: a class of antidiabetes drugs (e.g., metformin [Glucophage]) that increase cell sensitivity to insulin and decrease glucose production by the liver.
bilateral: occurring on both sides of the body.
bile: a greenish fluid produced by the liver that aids in the digestion of fats and the excretion of toxins.
bile duct: a small passage that carries bile from the gall bladder, where it is stored, to the small intestine.
bilirubin: a yellowish pigment byproduct of hemoglobin released when red blood cells are broken down. Serum bilirubin is measured to gauge the health of the liver and gall bladder; a high bilirubin level (hyperbilirubinemia) is characterized by jaundice (yellowing of the skin and whites of the eyes), dark urine, and clay-colored stools.
bioavailability: the degree to which a drug or other substance is absorbed and circulated in the body.
biochemical response: a favorable response to treatment as indicated by normalization of blood values (e.g., liver enzyme levels).
bioelectrical impedance analysis (acronym BIA): a method of analyzing body composition, including body fat and lean body mass. BIA measures resistance to an electrical current passed through the body; greater resistance indicates a higher percentage of fat.
biopsy: the removal of a small sample of cells or tissue for microscopic examination and/or culture, typically for diagnostic purposes.
biotechnology: industrial processes that involve the use of biological systems or products (e.g., monoclonal antibodies, genetically engineered recombinant proteins).
biotin: a B-complex vitamin needed for normal metabolism of nutrients.
bipolar disorder: manic-depression; a psychiatric condition characterized by alternating cycles of elevated and depressed mood.
blastogenesis: the production and maturation of new lymphocytes in response to infection.
blinding: a technique for reducing bias in clinical trials by ensuring that participants do not know who is receiving an experimental therapy, a standard (control) treatment, or a placebo. In a single-blind study, the subjects do not know what treatment--if any--they are receiving; in a double-blind study, neither the subjects nor the researchers administering the therapy know who is receiving what treatment.
blip: a transient, often small, increase in viral load, liver enzymes, or some other laboratory value.
blood chemistry panel (aka chem screen): a set of tests used to measure levels of various substances (e.g., liver enzymes, electrolytes) in the blood.
blood transfusion: the infusion of donated blood or blood components for the treatment of a medical condition (e.g., anemia, loss of blood due to injury or surgery).
blood-borne: refers to pathogens transmitted through direct blood-to-blood contact, for example, via shared needles or blood transfusion.
blood-brain barrier: a physical barrier between the blood vessels and the brain that is selectively permeable (allows only certain substances to pass through). Many drugs do not cross the blood-brain barrier and therefore cannot be used to treat infections within the central nervous system.
bloodwork: laboratory tests that assess properties of the blood. See also blood chemistry panel. See also complete blood count.
body fat redistribution syndrome: See lipodystrophy.
body mass index (acronym BMI): a measure of body mass that is calculated as weight divided by height squared.
bone marrow: the soft, spongy tissue in the interior of certain bones (e.g., the long bones of the limbs); bone marrow contains stem cells and is the site of blood cell production.
bone marrow suppression (aka myelosuppression): damage to the blood-producing stem cells in the bone marrow, which may be caused, for example, by drugs, toxic chemicals, or radiation; bone marrow suppression decreases blood cell production, which can lead to reduced immune function, anemia, poor blood clotting, and other conditions.
booster: a subsequent dose of a vaccine or drug given some time after the initial administration to enhance or restore its effectiveness.
boosting: use of one drug to increase blood levels, and thus enhance the activity, of another drug; small amounts of ritonavir are commonly used to boost levels of other protease inhibitors.
branched-chain DNA (bDNA) assay: a test that measures the amount of virus in plasma or tissues (viral load) using a chemical signal produced by viral genetic material.
brand name: the name under which a drug is commercially marketed.
breakthrough: a condition that develops despite measures to prevent it; occurrence or recurrence of an infection or cancer while undergoing treatment. See also viral breakthrough.
broad-spectrum antibiotic: an antibiotic drug active against a range of different bacteria.
budding: the emergence of newly produced virus particles through a host cell membrane.
buffalo hump: See dorsocervical fat pad.
buffer: a substance added to a drug to make it easier to absorb, to prevent damage from stomach acid, or to reduce stomach discomfort.
butyl nitrite:
See nitrite inhalant.
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