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AIDS Glossary
t cells ***
White blood cells that play an important part in the immune system. There are three different types of T cells, each of which has different subsets. The commonly measured T cells are helper T cells, killer T cells, and suppressor T cells.
t.i.d.
pharmaceutical abbreviation,  three times a day (ter in die)
t.i.w.
pharmaceutical abbreviation,  three times a week
t4 cell
see CD4 cell.
t8 cell
see CD8 cell.
tachycardia
very rapid heartbeat.
tagamet
brand name of cimetidine.
tal.
pharmaceutical abbreviation,  of such (talis)
tat
transactivator of transcription, a gene of HIV that plays a role in viral replication by regulating the transcription of viral DNA into RNA; also the protein produced by that gene.
tat inhibitor
a drug that inhibits HIV replication by interfering with the tat protein.
tb
abbreviation,  tuberculosis. a bacterial infection.
t-cell (t-lymphocyte)
a white blood cell derived from the thymus that contributes to the cell-mediated immune response. There are 3 major types of T-cells: T-helper (CD4 cells), T-suppressor (CD8 cells) and T-killer (cytotoxic T-lymphocytes or CTL). Contrast with B-cell.

t-cell growth factor
see interleukin-2.
t-cell receptor
a structure made up of several proteins located on the surface of T-cells. The receptor recognizes antigens bound to major histocompatibility (MHC) molecules and triggers various cellular functions important to immune responses.
tcid50
tissue culture infecting dose. The level of dilution of a virus at which half of a series of laboratory wells contain active, growing virus.
tcm
see Traditional Chinese Medicine.
telomere
a complex of repetitive DNA sequences that cap the ends of chromosomes. Telomeres play a role in cellular replication via the telomerase enzyme, which helps determine whether cells are able to replicate. Telomeres shorten each time a cell divides, and signal cell senescence (loss of function) when they reach a critical length.
teratogenicity
the ability to cause malformation of the fetus (birth defects).
testis (testicle)
one of the male gonads located in the scrotal sac that are the site of sperm production.
testosterone
a steroid hormone produced by the testes and adrenal glands. Testosterone is required for sperm production, the development of the male reproductive organs, and the emergence of male secondary sexual characteristics. The hormone is also required for the buildup of lean muscle mass. Testosterone levels are often low in HIV positive men; the hormone is under study as a therapy for wasting syndrome. Possible side effects include acne, mood swings, change in sex drive, liver toxicity, prostate enlargement and masculinization in women.
tetanus
a life-threatening disease caused by toxins produced by the bacterium Clostridium tetani, which often grow at the site of a cut or wound. Muscles first become stiff, then rigidly fixed (lockjaw). Vaccination against tetanus should be done every 10 years or at the time of injury.
tetracycline (achromycin, sumycin)
a broad spectrum antibiotic drug used to treat bacterial infections.
th naive
see naive T-cell.
th0 response
an immune response that involves aspects of both TH1 and TH2 branches of the immune system. TH0 cells produce cytokines that are characteristic of both TH1 and TH2 response.
th1 immune response
one of the branches of the immune system. The TH1 response involves a subset of CD4 lymphocytes called TH1 cells that secrete IL-1, IL-2 and gamma interferon, and which enhance the cell-mediated immune response (action of CTL and natural killer cells) and inhibit TH2 cell activity and the humoral immune response . TH1 activity is especially effective against agents that have infected cells (e.g. cell-associated HIV).
th2 immune response
one of the branches of the immune system. The TH2 response involves the TH2 subset of CD4 cells that secrete IL-4 and IL-10, and which enhance humoral immune response (antibody production) and inhibit TH1 activity and cell-mediated immune response. TH2 activity is most effective against microorganisms that are free-floating in the bloodstream (e.g., cell-free HIV).
thalamus

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one of the basal ganglia (a cluster of nerve cell bodies) deep in the brain that serves as a center for the relay of sensory information (especially pain and pleasure information) and plays a role in arousal.
thalidomide (synovir)
a sedative drug under investigation for treatment of aphthous ulcers, wasting syndrome and other conditions in persons with HIV disease. Thalidomide has been shown to reduce levels of tumor necrosis factor-alpha (TNF-alpha) in vitro. The drug has teratogenic effects and may cause severe birth defects; other side effects include skin rashes and peripheral neuropathy.
thc
see delta-9 tetrahydrocannabinol.
t-helper cell
see CD4 cell.
t-helper cell (t4 cell, cd4 cell) ***
A subset of T cells. Physicians regularly measure T-helper cell counts in HIV positive people. The normal range for T-helper cells is 480-1800, but may vary.
therapeutic vaccine (treatment vaccine)
a vaccine given after infection to reduce or arrest disease progression. Therapeutic vaccines are given to produce or reinforce an immune response in a person who is already infected. Contrast with preventive vaccine.
therapeutic widow (therapeutic ratio)
the range of dosages of a drug that achieve clinical efficacy but do not cause intolerable side effects; the difference between the minimum and maximum effective doses.
thiamine (vitamin b1)
see vitamin B
thrombocyte (platelet)
a type of blood cell that facilitates normal blood clotting.
thrombocytopenia
an abnormally low number of thrombocytes (platelets); the condition may result in abnormal bleeding and bruising. The normal platelet range is 150,000-300,000 per millimeter of blood. Thrombocytopenia may be controlled by the administration of certain cytokines or by removal of the spleen.
thrombosis
formation or presence of a clot within a blood vessel.
thrush
See candidiasis.
thymic factor (thymic hormone)
a hormone or cytokine (e.g., thymodulin, thymopentin, thymostimulin) produced by the thymus gland that is involved in the regulation of immune function.
thymic humoral factor
a peptide hormone isolated from calf thymus under study as an immunomodulatory treatment for HIV disease.
thymidine kinase
an enzyme that catalyzes the transfer of phosphate groups and is necessary for the transformation and metabolism of nucleoside analog drugs.
thymine (t)
one of the pyrimidine nucleic acid bases that make up nucleotides, the building blocks of DNA (but not RNA). The antiviral drugs AZT and d4T are nucleoside analogs associated with thymine.
thymus (adjective thymic)
a lymphoid organ located in the chest behind the sternum. The thymus is a source of T-lymphocytes in children, but generally shrinks during adolescence. The thymus is the site of T-lymphocyte differentiation, where the cells learn to recognize antigens. The thymus produces some 30 hormones or thymic factors (e.g., thymodulin, thymopentin, thymostimulin) that are involved in the regulation of immune function.
thymus ***
The organ of the body that trains T cells to be part of the immune system.
thyroid gland
an organ at base of the neck that produces thyroxin and other hormones.
thyroid stimulating hormone (tsh)
a pituitary hormone which stimulates the growth and function of the thyroid gland.
tibo derivative
a synthetic compound derived from molecules similar to valium and related tranquilizers. TIBO derivatives have been shown to have potent anti-HIV-1 activity by blocking the production of reverse transcriptase.
tid
3 times per day.
tincture
a substance that colors, dyes or stains. Also refers to a medicinal preparation of an active ingredient or extract (e.g., of a plant) dissolved in alcohol.
tine test
a skin test used to determine previous infection with tuberculosis; the tine test is an older test that has largely been superseded by the more accurate PPD test.
tinea
a group of infections of the skin, nails or hair caused by fungal organisms that typically cause a red, itchy rash. Types include tinea versicolor, tinea corporis (ringworm), tinea pedis (athlete's foot) and tinea cruris (jock itch).
tinnitis
an abnormal ringing or buzzing in the ears. Tinnitis may be a side effect of certain medications.
titer (titre)
a standard measure of the strength or concentration of a component per volume of a solution.
titration
the measurement of volume; often used to refer to the determination of a drug dosage.
tiw
3 times per week.
t-killer cell
see cytotoxic T-lymphocyte.
t-killer cell (cytoxic t cells) ***
A type of white-blood cell that kills foreign organisms after being activated by T-helper cells.
tmp-smx
see trimethoprim-sulfamethoxazol.
tnf
abbreviation,  tumor necrosis factor. a naturally occuring protein. TNF destroys cancer cells, but is suspected as being a co-factor in HIV replication.
tocopherol
see vitamin E.
tolerance
a condition in which the body becomes accustomed to an agent (e.g., drug) so that the previous dose no longer produces the desired effects and a progressively larger dose is needed to achieve a previously observed effect. See also cross-tolerance.
tonsil
one of 2 small immune system glands made up of lymphoid tissue, located at the back of the throat.
topical
pertaining to the surface of the skin; a medication applied to the skin.
topotecan
a topoisomerase inhibitor drug under study as an anti-HIV therapy.
total parental nutrition (tpn)
see parenteral nutrition.
toxicity (adjective toxic)
the quality of being poisonous or harmful; often used to refer to side effects of drugs.
toxicology
the study of the harmful effects of substances on the body, including the level of toxicity, the mechanism by which toxicity occurs and how it can be controlled.
toxicosis
a pathological condition resulting from poisoning.
toxin
a harmful or poisonous agent.
toxoplasmic encephalitis (cerebral toxoplasmosis)
see toxoplasmosis.
toxoplasmosis (toxo)
an opportunistic infection caused by the microscopic protozoan Toxoplasma gondii, found in undercooked meat and cat feces. Symptoms may include headache, lymphadenopathy, malaise, muscle pain and fever. A common manifestation of the disease toxoplasmic encephalitis (cerebral toxoplasmosis), characterized by brain swelling, dementia, confusion, lethargy, seizures and coma; the eyes, heart and lungs may also be affected. Toxoplasmosis is treated with pyramethamine, usually in combination with other drugs; TMP-SMX may be used as prophylaxis.
toxoplasmosis ***
An inflammation of the brain caused by toxoplasma gondii, a parasite. Frequently causes inflammation of the brain. It may also involve the heart, lung, adrenal glands, pancreas and testicles. This disease is usually mild but it can cause fever and swollen glands, as well as severe headaches. Fifty percent of Americans have been exposed to toxoplasma gondii at some point in their lives. This is considered an AIDS-defining condition in the United States.
tpn
see total parenteral nutrition.
trace element
a substance needed in very small amounts for the proper functioning of the body. There are 7 known trace elements: chromium, copper, cobalt, iodine, iron, selenium and zinc.
trachea
the windpipe; the tube that extends from the oral cavity into the chest, where it branches into the 2 major bronchial tubes.
tract
an organ system that allows the body to interact with the outside world (e.g., gastrointestinal tract, respiratory tract); also a bundle of nerve fibers (e.g., extrapyramidal tract).
traditional chinese medicine (tcm)
an Asian system of healing that focuses on achieving internal balance. TCM practitioners use methods such as acupuncture, heat application (moxibustion), herbal preparations and exercises (e.g., tai chi, qigong) to restore the flow of qi (vital energy) and the balance of yin and yang. TCM diagnosis is based on examination of the pulse and tongue. TCM diagnostic patterns typically seen in persons with HIV/AIDS are spleen qi deficiency, liver qi congestion, general qi deficiency and yin deficiency.
trans- (prefix)
across, through or between.
transactivation
a situation in which one gene product causes a different gene to be activated.
transactivator of transcription
see tat.
transaminase
an enzyme used as a catalyst in moving an amino acid from one compound to another. Doctors use a transaminase lab test to indicate liver function.
transaminase (aminotransferase)
an enzyme (e.g., SGOT [AST], SGPT [ALT]) produced by the liver that catalyzes the transfer of amino acids. Abnormally high levels in the blood indicate liver disease or damage (e.g., hepatitis, drug-related liver toxicity).
transcription
the first step in protein synthesis and replication. Genetic information encoded in DNA is copied to messenger RNA, which is used as a template for the production of new proteins.
transcutaneous (transdermal)
able to be absorbed by or to pass through intact skin; administered through the skin.
transdominant mutant
genetically engineered, non-functional copies of HIV viral proteins that compete with functional HIV for the various molecules needed for viral replication.
transduced autologous fibroblasts (taf)
a type of gene therapy for HIV disease. Fibroblasts (collagen-producing cells) are removed from the body, genetically altered and reinfused into the body in an attempt to enhance the anti-HIV immune response.
transduction
the introduction of a transferred gene into a cell via genetic engineering techniques (e.g., a virus vector, liposomes).
transfer factor
a substance produced by white blood cells that transfers the ability to recognize foreign invaders from cell to cell.
transformation zone
the area of the cervix where squamous cells and columnar cells meet; a common site of dysplasia.
transfusion
the transfer of blood or blood components from one individual to another (or back to the donor in the case of autologous transfusion).
transgenic
pertaining to a chromosome or an organism into which genes from another individual have been inserted.
transient
short-lived; not permanent.
treatment arm
a group of participants in a research trial who all receive the same treatment. Contrast with control arm.
treatment investigational new drug (tind)
a FDA classification that allows physicians to prescribe certain promising experimental drugs prior to marketing approval for patients with life-threatening diseases who lack other treatment options. See also investigational new drug.
treatment vaccine
see therapeutic vaccine.
trental
brand name of pentoxifylline.
treponema pallidum
the spiral-shaped bacteria that causes syphilis.
tretinoin
see retinoic acid.
trial (study)
an experiment involving the collection, analysis and interpretation of data, for example a clinical trial to determine the safety and efficacy of a new drug.
triazole
see azole drug.
trichomoniasis (tv)
infection with the protozoan parasite Trichomonas vaginalis. Trichomoniasis may be asymptomatic, especially in men; in women symptoms may include vaginal irritation, itching, discharge and painful urination.
trichosanthin (compound q, glq223)
the active ingredient derived from the root of the Chinese cucumber plant. Trichosanthin has been studied as an anti-HIV therapy and has been shown to kill HIV-infected macrophages. Side effects may be severe, and include muscle and joint pain and central nervous system complications.
triglyceride
a combination of glycerol and fatty acids.
triglycerides
fat in the blood. A high triglyceride blood test can indicate liver or pancreas problems. A low result can indicate malnutrition.
trimester
a 3-month period; usually used to refer to one-third of the length of a normal human pregnancy.
trimethoprim-sulfamethoxazole (tmp-smx, bactrim, s
an antibiotic drug combination. TMP-SMX is the preferred first-line therapy for prophylaxis and treatment of PCP, and may be effective against other OI such as toxoplasmosis. Side effects include fever, nausea, diarrhea, photosensitivity, skin rash and neutropenia. Desensitization to the drug is often possible using slowly increasing dosages.
trimetrexate (neutrexin)
an antifolate drug used as salvage therapy for people with PCP who fail standard treatments. Trimetrexate can cause severe bone marrow toxicity, and is typically used in conjunction with leucovorin to protect against anemia.
trophoblast
the layer of cells covering the embryo that develops into the placenta.
tropism
affinity for or the tendency to move toward something; the specific attraction of a virus or other microorganism to a particular host tissue, determined in part by host cell surface markers (e.g., some HIV strains have a tropism for CD4 cells).
trough level
the lowest concentration of a drug reached in the body between dosages.
t-suppressor cell
a type of T-cell bearing the CD8 surface marker. T-suppressor cells helps to regulate and control immune system activity by inhibiting antibody production and CTL activity.
t-suppressor cell (t8 cell, cd8 cell) ***
A type of white blood cell that helps control the body's response to an infection.
tubal ligation
a method of permanent female sterilization in which the fallopian tubes are cut.
tubercle
a granulomatous, spherical lesion containing a concentration of white blood cells, characteristic of infection with Mycobacterium tuberculosis.
tuberculin reactive
refers to someone who tests positive for exposure to tuberculosis on a PPD skin test.
tuberculin skin test
a skin test for exposure to tuberculosis. See PPD test.
tuberculosis
a bacterial infection.
tuberculosis (tb)
an infectious disease caused by Mycobacterium tuberculosis that typically affects the lungs, but may also occur in other organs (extrapulmonary TB). Transmission generally occurs through inhalation of aerosolized sputum droplets. A combination of 4 chemotherapeutic drugs is standard therapy. Multidrug-resistant tuberculosis (MDR-TB) is resistant to several standard drugs and requires more aggressive treatment.
tubo-ovarian abscess
a inflammation of the a fallopian tube and the companion ovary, characterized by swelling and accumulation of pus.
tubule
a small, narrow tube or anatomical channel.
tumor
a neoplasm; a new growth of rapidly proliferating cells. Tumors may be either benign or malignant (cancerous).
tumor necrosis factor
a naturally occuring protein, commonly called TNF. TNF destroys cancer cells, but is suspected as being a co-factor in HIV replication.
tumor necrosis factor (tnf, cachectin)
a cytokine, produced by activated monocytes and macrophages, that can destroy tumors. When chronically elevated (as may occur in HIV disease), TNF-alpha may lead to fever, anorexia, hypermetabolism and wasting. TNF-alpha may block the production of enzymes that digest fats, leading to the breakdown of muscle tissue. In laboratory tests TNF-alpha has been shown to stimulate HIV replication. Some drugs (e.g., thalidomide, ketotifen) reduce TNF-alpha levels. TNF-beta is released by CD4 and CD8 T-cells when stimulated by an antigen. VERIFY TNF-BETA.
tx
medical abbreviation for treatment.
tyrosine kinase
an enzyme that promotes various cellular processes by attaching phosphates to other molecules.
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