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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MAB: See monoclonal antibodies.
MAC: See Mycobacterium avium.
macaque: a type monkey often used in scientific research.
macro-: prefix meaning large.
macrolide: a class of antibiotic drugs (e.g., clarithromycin, azithromycin).
macrophage: a large scavenger white blood cell (phagocyte) that ingests and processes foreign invaders and cellular debris; macrophages secrete chemical messengers (monokines) that coordinate a variety of immune responses. Macrophages are derived from monocytes that leave the blood and migrate into the tissues; specialized macrophages protect the skin, lungs (alveolar macrophages), brain (microglia), liver (Kupffer cells), and other tissues.
macrophage colony-stimulating factor (acronym M-CSF): a cytokine that stimulates the production of macrophages.
magnesium (acronym mg): a mineral necessary for proper metabolism.
magnetic resonance imaging (acronym MRI): a sensitive, noninvasive method for viewing soft tissues of the body using a strong magnetic field.
MAI: See Mycobacterium avium complex.
maintenance therapy (aka secondary prophylaxis): suppressive therapy that follows successful initial treatment of an illness (induction therapy); ongoing therapy used to prevent disease recurrence.
major histocompatibility complex (acronym MHC): a group of genes that control the expression of cell surface protein markers (human leukocyte antigen, or HLA markers) that allow immune cells to recognize components of the body (i.e., to distinguish "self" from "non-self"); MHC markers are necessary for antigen presentation and recognition of antigens by immune cells.
malabsorption: decreased absorption of nutrients by the intestines.
malaise: a generalized feeling of illness or discomfort; a flu-like feeling.
malignancy: cancer; cells that grow in an uncontrolled manner and may invade nearby tissue or metastasize (spread) to other sites in the body.
malignant: severe, harmful; tending to steadily worsen or grow uncontrollably. Contrast with benign.
malnutrition (aka malnourishment): lack of the minimum amount of proteins, carbohydrates, lipids, vitamins, minerals, and other nutrients essential for health and proper growth.
manic-depression: See bipolar disorder.
mantoux test: See tuberculin skin test.
marker: a unique identifier on a cell’s surface; also refers to a laboratory result or clinical observation that suggests presence or progression of a disease. See also surrogate marker.
mast cell: a type of immune cell (granulocyte) that mediates allergic reactions; mast cells release chemicals including histamine and heparin.
maximum tolerated dose: the largest dose of a drug an individual can take without unacceptable adverse side effects.
mean (aka average): a statistical measurement of the central tendency, or average, of a set of values. For example, in the series “1, 1, 1, 2, 2, 10, 32,” the mean is 7 (determined by adding all the values and dividing by the number of values). Compare with median.
median: the middle value in a distribution; the number within a series that is preceded and followed by an equal number of values. For example, in the series “1, 1, 1, 2, 2, 10, 32,” the median is 2 (there are three values lower and three values higher). Compare with mean.
megadose: a much larger than normal dose.
megaHAART: a salvage regimen that employs multiple (usually five or more) antiretroviral drugs.
megakaryocyte (aka thromboblast): a large precursor cell in the bone marrow that gives rise to thrombocytes (platelets).
megestrol acetate (brand name Megace): a synthetic progesterone used to stimulate appetite and promote weight gain in individuals with wasting syndrome.
membrane: a thin sheet or layer of pliable tissue serving as a semipermeable covering.
memory cell: a long-lived B cell or T cell that is specialized to recognize and respond to a specific pathogen; memory cells remain in the body after an initial immune response, and are primed to respond to a subsequent attack by the same invader. Compare with naive T cell.
meningitis: inflammation of the meninges, the membranes that cover the brain and spinal cord.
menopause: cessation of menstruation.
menstrual cycle: the monthly human female reproductive cycle that involves the maturation of an ovum, its release from the ovary, the buildup of the uterine lining, and (if the ovum is not fertilized) the shedding and discharge of uterine blood and tissue (menstruation).
messenger RNA (acronym mRNA): See ribonucleic acid.
meta-analysis: a type of analysis that combines data from a number of different trials (e.g., several clinical trials looking at the same drug).
metabolic acidosis: a disturbance of the body’s acid-base balance, resulting in an elevated acid level (low pH); the condition may be due to a variety of causes, including diabetes mellitus, kidney dysfunction, and drug toxicity. See also lactic acidosis.
metabolic syndrome (aka syndrome X): a constellation of metabolic manifestations that may include insulin resistance, blood glucose abnormalities, elevated triglycerides, low HDL (?good?) cholesterol, high blood pressure, and visceral abdominal obesity; the syndrome is associated with increased risk of cardiovascular disease.
metabolism (adjective metabolic): the processes of building the body's molecular structures from nutrients (anabolism) and breaking them down for energy (catabolism); also refers to the chemical breakdown of drugs and toxins within the body.
metabolite: a chemical product of metabolism.
metastasis (adjective metastatic): spread of a disease manifestation from one body site to another, in particular the spread of cancer.
methadone: an oral opioid drug used for pain relief and to treat opiate (e.g., heroin) addiction; methadone maintenance therapy prevents opiate withdrawal symptoms by administering small doses of methadone on a regular (e.g., daily) basis.
methamphetamine (aka crystal): a drug that stimulates the central nervous system, leading to increased energy and decreased appetite.
MHC: See major histocompatibility complex.
micro-: prefix meaning small, or one-millionth.
microbe: a tiny living organism (e.g., bacterium, protozoan, fungus), in particular those that cause disease.
microbicide: an agent that inactivates, kills, or destroys microbes; vaginal and anal microbicides are under study as a means of preventing transmission of HIV and other sexually transmitted infections.
microgram (acronym mcg): one-millionth of a gram.
micron: one-millionth of a meter, or one-thousandth or a millimeter.
micronutrient: a trace element; an organic compound (e.g., vitamin or mineral) required in small amounts for physical health, growth, and metabolism.
microorganism: a tiny organism (e.g., bacterium, virus).
microsporidiosis: infection with a protozoan parasite of the Microsporidia family (e.g., Enterocytozoon bieneusi, Septata intestinalis), which may affect the sinuses, lungs and intestines in immunocompromised individuals.
milligram (acronym mg): one-thousandth of a gram.
milliliter (acronym ml): one-thousandth of a liter, the unit of measurement typically used for viral load.
millimeter (acronym mm): one-thousandth of a meter; mm3 denotes a cubic millimeter, the unit of measurement typically used for CD4 cell counts.
mineral: an inorganic element that promotes chemical reactions within the body and is necessary for proper cellular metabolism; essential minerals include calcium, iodine, iron, magnesium, potassium, and zinc.
MIP-1 alpha, MIP-1 beta (aka macrophage inflammatory protein): two chemokine proteins that, in association with RANTES, bind with the CCR5 cell surface receptor and inhibit the entry of HIV into host cells.
mitochondria (singular mitochondrion): energy-producing organelles (small organs) located in the cytoplasm of cells.
mitochondrial toxicity: damage to the mitochondria as a side effect of drugs (including nucleoside and nucleotide reverse transcriptase inhibitors), which can lead to lactic acidosis.
molecule: a small unit of matter made up of atoms; the smallest unit of a substance that retains its unique characteristics.
molluscum contagiosum: a viral skin condition characterized raised, flesh-colored lesions with a central depression, most often appearing on the face, neck, arms, legs, and anogenital region.
monoamine oxidase inhibitor (acronym MAOI): See antidepressant.
monoclonal antibodies (acronym MABs): antibodies derived (often by genetic engineering) from a single clone of cells; MABs are specifically directed against a particular epitope (a unique antigen marker that can trigger an antibody response) and are used as tools to detect and identify specific proteins.
monocyte: a large white blood cell that plays a role in immune defense. Monocytes circulate in the bloodstream; when they migrate to the tissues, they mature into macrophages.
mononuclear cell: a cell with a single nucleus; a subset of white blood cells (e.g., lymphocytes, monocytes).
mononucleosis (aka kissing disease): an infectious disease caused by the Epstein-Barr virus (EBV) that is easily transmitted via saliva; the disease is characterized by a sore throat, fatigue, and possibly swollen lymph nodes or spleen.
monotherapy: use of a single drug or other therapy.
mood: emotional or psychological state.
morbidity: sickness; the state of being affected by disease.
mortality: death; the mortality rate is the rate of death in a given population.
mother-to-child transmission (acronym MTCT, aka perinatal transmission, aka vertical transmission): transmission of a pathogen from a mother to a fetus or newborn in utero (in the womb), intrapartum (during birth), or postpartum (after birth, for example via breast-feeding). Compare with horizontal transmission.
MRI: See magnetic resonance imaging.
MTCT: See mother-to-child transmission.
M-tropic: refers to strains of HIV that preferentially infect monocytes and macrophages. Compare with T-tropic.
mucosa: See mucous membrane.
mucosal immunity: immunity that involves IgA antibodies located in the mucous membranes at the openings of the body (e.g., the genital tract).
mucous membrane (aka mucosa): a moist layer of semipermeable tissue lining the openings of the body (e.g., the gastrointestinal, respiratory, and genitourinary tracts).
mucus: a thick, viscous fluid secreted by mucous membranes that acts as a protective barrier and lubricant.
multifocal: present or occurring at more that one site.
multivariate analysis: a statistical analysis technique in which multiple variables are analyzed simultaneously, with correction for confounding associations, to determine the contribution made by each variable to an observed outcome. Compare with univariate analysis.
musculoskeletal: refers to the muscles and the skeletal system.
mutation: a change in the character of a gene that is perpetuated when a cell divides or a virus replicates; a mutant is a new strain of an organism produced by a genetic mutation.
myalgia: muscle pain.
mycobacteria: a category of gram-positive, acid-fast bacteria that cause diseases such as tuberculosis, leprosy, and Mycobacterium avium complex.
Mycobacterium avium (acronym MAC): an opportunistic illness caused by Mycobacterium avium or Mycobacterium intracellulare (sometimes referred to as Mycobacterium avium-intracellulare, or MAI), bacteria found in soil and water. In immunosuppressed persons (usually with
Mycobacterium tuberculosis: acid-fast bacteria cause tuberculosis.
mycosis: a disease caused by fungus
myelin: a white, fatty substance that forms a sheath around nerve fibers and provides insulation necessary for proper neural transmission.
myelocyte: a type of immature white blood cell normally found in the bone marrow.
myeloma: a cancer of the bone marrow.
myelopathy: a disease or disorder of the spinal cord, or of the blood cell-producing tissues and cells in the bone marrow.
myelosuppression: See bone marrow suppression.
myelotoxic: destructive to the bone marrow.
myocardial infarction (acronym MI, aka heart attack): death or damage to a section of the heart muscle due to a lack of oxygen, typically caused by the blockage of the coronary arteries that supply the heart.
myocardium (adjective myocardial): the muscle layers of the heart.
myopathy: disease or degeneration of the muscles.
myositis: inflammation of the skeletal muscle.
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