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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iatrogenic: refers to an unfavorable response to medical or surgical treatment; a condition attributable to medical therapy.
IC50, IC90: See inhibitory concentration.
IDDM: See diabetes.
idiopathic: refers to a disease or condition of unknown cause or origin.
IDU: See injection drug user.
IFG: See impaired fasting glucose.
IFN: See interferon.
IGT: See impaired glucose tolerance.
immune deficiency (aka immunodeficiency): inability of the immune system to function properly, resulting in increased susceptibility to opportunistic illnesses and cancers; immunodeficiency may be either congenital (present from birth) or acquired, as with HIV/AIDS.
immune modulator (aka immunomodulator): an agent (e.g., cytokine, interferon) or process that modifies or enhances the activity of the immune system. See also immunotherapy.
immune restoration (aka immune reconstitution): restoration of immune system function; rebuilding a damaged or compromised immune system.
immune restoration syndrome (aka immune recovery syndrome, acronym IRS): temporary exacerbation of symptoms due to recovery of immune function; IRS occurs because some disease manifestations (e.g., liver inflammation) are caused by an immune response to a microorganism, rather than the action of the pathogen itself.
immune system: the defense system that protects the body against foreign invaders (such as microorganisms) and cancerous cells. The immune system has two branches, nonspecific (innate) and specific (adaptive); the latter is further divided into cell-mediated (Th1) immunity and humoral (antibody-mediated, or Th2) immunity. Immune system organs include the lymph nodes, spleen, thymus, and tonsils.
immune-based therapy: See immunotherapy.
immunity: resistance to disease; the body’s ability to recognize and defend against pathogenic organisms and cancerous cells.
immunization: the process by which an individual is protected against infection by a disease-causing microorganism. In active immunization (vaccination), a person is exposed to a small amount of a killed or inactivated microorganism or its proteins in order to stimulate an immune response; in passive immunization, a person is given manufactured antibodies or antibodies transferred from another individual.
immunocompetent: capable of mounting an immune response.
immunocompromise: reduced immune system function.
immunogenicity: the ability to stimulate an immune response.
immunoglobulin: See antibody.
immunology (adjective immunological): the medical specialty concerned with the immune system and its disorders.
immunosuppression: a condition in which immune defenses have been suppressed, damaged, or weakened; an immunosuppressive drug (e.g., cyclosporine, tacrolimus) is one that reduces or dampens immune function.
immunotherapy (aka immune-based therapy): therapy that attempts to modify or enhance immune response, or reconstitute a damaged immune system. Examples include active immunization (vaccination), CD4 cell expansion, and cytokine therapy. See also immune modulator.
impaired fasting glucose (acronym IFG): a condition characterized by moderately elevated fasting blood glucose; IFG is defined as a fasting glucose level of 110–125 mg/dL.
impaired glucose tolerance (acronym IGT): a condition in which the body does not produce enough insulin, or cells do not respond to insulin efficiently (insulin resistance); IGT is defined as a glucose level of 140–199 mg/dL after an oral glucose tolerance test.
impairment: dysfunction, damage, or deterioration.
in situ: occurring in place or at a specific site; carcinoma in situ is a tumor that has not invaded surrounding tissues.
in utero: in the uterus; typically refers to events that occur in the womb before birth.
in vitro: Latin for "in glass"; refers to studies done in a test tube or culture medium in the laboratory.
in vivo: Latin for "in the body of a living organism"; refers to studies done using human or animal subjects.
incidence (aka incidence rate): the number of new cases of a disease or condition in a specific population during a given period; the incidence rate is determined by dividing the number of new cases by the total population. Compare with prevalence.
inclusion criteria: See enrollment criteria.
incubation period: the period of time between an initial exposure to an infectious pathogen and the development of disease symptoms.
indication: the use for which a drug is intended and approved.
indinavir (brand name Crixivan): a protease inhibitor drug approved for use as part of combination antiretroviral therapy to treat HIV disease.
indolent: sluggish, slow to develop.
induction: promotion or acceleration of enzyme activity.
induction therapy: a short course of therapy used to control active disease, usually requiring higher and/or more frequent doses than are used after the disease is brought under control. Compare with maintenance therapy.
inert: inactive; having no biological or catalytic activity.
infection: a condition in which the body is invaded by an infectious microorganism (e.g., bacteria, virus, fungus).
infectious: capable of being transmitted from person to person.
inflammation: the body's response to tissue injury or infection, which typically includes increased blood vessel dilation and permeability, resulting in redness, swelling, heat, and pain.
influenza: the flu; an infectious viral respiratory disease characterized by chills, fever, prostration, headache, muscle aches, sore throat, and a dry cough.
informed consent: a mechanism designed to protect subjects in clinical trials. Before entering a trial, participants must sign a form stating that they have been given and understand important information about the trial and voluntarily agree to take part.
infusion: the direct injection of a substance (e.g., drug, nutrient) into the bloodstream.
inhibitor: an agent that inhibits or blocks an activity.
inhibitory concentration (aka inhibitory dose, aka effective concentration or dose): a measure of drug efficacy. The IC50 (ID50/EC50/ED50) is the median effective dose, or the concentration of a drug that produces 50% suppression of viral replication or eliminates 50% of a population of microorganisms. The IC90 (ID90/EC90/EC50) produces 90% viral suppression or eliminates 90% of microorganisms.
inhibitory quotient (acronym IQ): a measure of drug exposure and susceptibility in an individual. The IQ is typically calculated as the minimum drug concentration (Cmin) divided by the IC50 (the drug concentration that achieves 50% suppression of viral replication).
injection drug user (acronym IDU): a person who uses a drug (e.g., heroin, cocaine, speed) administered with a needle and syringe; a more general term than intravenous drug user (IVDU), which refers to a specific method of drug injection.
innate immunity: See nonspecific immunity.
inoculation: the introduction of an agent, pathogen, or antigen into the body.
insomnia: inability to sleep.
institutional review board (acronym IRB): a committee of physicians, medical experts, researchers, and community members that is responsible for ensuring that clinical trials conducted by a hospital or other institution are safe and ethical.
insulin: a hormone produced by beta cells in the Islets of Langerhans in the pancreas; insulin enables cells to take up and use glucose.
insulin resistance: a condition in which the body's cells cannot properly use insulin, leading to blood glucose abnormalities. See also diabetes.
integrase: a viral enzyme that enables the virus to insert its genetic material into a host cell's DNA.
integrase inhibitor: an antiviral drug that blocks viral replication by interfering with the action of the integrase enzyme.
integration: the process by which viral DNA is integrated into, or made part of, the genetic material of a host cell.
intent-to-treat (ITT) analysis: a method of analyzing the results of a clinical trial in which all participant originally assigned to an arm are analyzed, including those who dropped out due to treatment failure or side effects. Compare with as-treated analysis.
interaction: See drug interaction.
intercurrent: occurring at the same time.
interferon (acronym IFN): one of a family of cytokines (messenger proteins), produced by infected cells or immune cells, that promote immune cell activity, protect cells from viral infection, discourage growth of cancerous cells, and/or interfere with viral replication. The three major classes of interferon are alpha, beta, and gamma; interferon-alpha (brand names Intron-A, Roferon-A, Infergen) is used to treat hepatitis B and C and certain types of cancer. See also pegylated interferon.
interleukin (acronym IL): one of a family of cytokines (chemical messengers), secreted by lymphocytes and macrophages, that promote immune cell activity and regulate a range of immune functions. There are some 30 known types of interleukin. IL-2 (brand names Aldesleukin, Proleukin) and IL-12 enhance Th1 immune responses and are under study as therapies for HIV disease. IL-3 stimulates blood cell production, while IL-8 promotes new blood vessel growth.
intermittent: occurring sporadically or in cycles.
international unit (acronym IU): a standard unit of measurement.
intima-media: inner and middle layers; typically refers to arteries, in particular the carotid artery in the neck. Thickening of the arterial intima-media is a marker for atherosclerosis and is used to predict coronary artery disease.
intolerance: inability of the body to tolerate the adverse side effects of a drug.
intra-: prefix meaning within.
intracellular: within a cell.
intractable: resistant to treatment.
intradermal: injected within the layers of the skin.
intraepithelial: within or among the cells of the tissues that cover body surfaces and line cavities, ducts and vessels.
intraepithelial neoplasia: abnormal growth of epithelial cells that may be a precursor to cancer; common sites include the uterine cervix and the anal canal. Abnormal cells may be detected using a Pap smear. Intraepithelial neoplasia is associated with certain strains of the human papillomavirus (HPV) and develops more often in people with compromised immune systems. See also squamous intraepithelial lesion.
intramuscular (acronym IM): administered into a muscle.
intrapartum: during birth.
intravenous (acronym IV): injected into a vein.
invasive: refers to a procedure that involves entry into or invasion of the body; also refers to a cancer that spreads from its original site to other parts of the body.
investigational new drug (acronym IND): an FDA classification applied to experimental drugs undergoing clinical trials to assess their safety and efficacy prior to marketing approval.
Invirase: hard-gel formulation of saquinavir.
iron: an important trace element needed for the production of red blood cells; iron deficiency can lead to anemia.
ischemia: reduced blood supply to body tissues.
islets of Langerhans: small glands within the pancreas that contain insulin-producing beta cells.
isolate: a specific individual microbe and its genetically identical progeny; a specific strain of HIV from a cultured cell line (laboratory isolate) or a human (primary isolate).
isoniazid (aka INH): an antibiotic used in combination regimens to treat tuberculosis.
ITT: See intent-to-treat (ITT) analysis.
IU: See international unit.
IV: See intravenous.
IVDU: See injection drug user.
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