cachexia

general wasting due to illness or stress.

caf

abbreviation,  see cell antiviral factor.

calcium

a metallic trace element essential for bone maintenance and proper neural and muscular function. Calcium is found in dairy products and leafy green vegetables.

calorie

a unit of measurement of heat or energy.

campylobacter

a family of bacteria (e.g., C. jejuni, C. fetus) that may cause acute illness affecting the small intestine, characterized by abdominal pain, nausea, vomiting, fever and bloody diarrhea. Campylobacter is frequently found in undercooked poultry and in raw or unpasteurized milk products.

canarypox

a poxvirus that typically infects canaries and is used in human vaccine research.

cancer

a group of diseases characterized by abnormal growth (neoplasm, tumor) and spread to other parts of the body (metastasism).

candida

A genus of yeast-like fungi. Some species of Candida are part of the normal flora of the mouth, intestines and vagina. Several species may cause infection in humans, especially immunocompromised persons, including C. albicans, C. tropicalis and C. krusei.

candidemia

the presence of Candida in the peripheral blood.

candidiasis

a fungus infection, caused by a member of the genus Candida. In the mouth, candidiasis is called thrush and shows up as white patches. In the vagina, the disease is called vulvovaginal candidiasis. Candidiasis can also attack lungs and the esophagus. This infection is considered an AIDS-defining condition in the United States.

canker sore

see aphthous ulcer.

cannabis

Cannabis sativa, a plant that contains the psychoactive ingredient delta-9 tetrahydrocannabinol (THC). Cannabis ingestion typically produces feelings of euphoria and/or drowsiness. Cannabis is used medically to reduce nausea due to chemotherapy and restore appetite in persons with wasting syndrome. (marijuana)

capillaries

tiny blood vessels that form the most distal part of the circulatory system. Arteries branch into ever smaller vessels, finally ending in the capillaries, which connect with the smallest branches of the veins. Capillaries deliver oxygen and nutrients to and remove waste products from the body's cells.

carbohydrate

an organic molecule composed mainly of carbon, hydrogen and oxygen atoms. Carbohydrates constitutes a major class of nutrients, and are present in foods such as bread and pasta.

carbon dioxide

a colorless, odorless gas. Carbon dioxide is a by-product of cellular metabolism that is eliminated by the lungs. Carbon dioxide levels in the blood determine the breathing rate and the blood's acid-base balance. (co2)

carcinogenesis

the development of cancer. A carcinogen is a chemical or physical agent (e.g., drugs, radiation) that facilitates the development of cancer. (adjective carcinogenic)

carcinoma

a malignant tumor of the epithelial cells that line body surfaces and cavities. Carcinoma in situ (CIS) refers to an early stage of cancer that has not invaded surrounding tissues.

cardiomyopathy

a degeneration of the heart muscle, thought to be caused by HIV or by some drugs.

cardiovascular

refers to the circulatory system (the heart and blood vessels).

carpal tunnel syndrome

a condition in which a nerve in the wrist becomes inflamed and presses against the bones that make up the carpal tunnel, often resulting in pain. Carpal tunnel syndrome is often caused by repetitive strain, and may also be a side effect of treatment with human growth hormone.

castleman's disease

a disease that causes benign enlargement (hyperplasia) of the lymph nodes.

CAT scan

see computed tomography scan.

cat scratch disease

see bacillary angiomatosis.

catabolism

the breakdown of bodily proteins for energy and raw materials. Excess catabolism results in wasting.

catalyst

an agent that promotes or accelerates a chemical reaction without itself being consumed.

category a, b, c (aids)

a system for classifying stages of HIV/AIDS. Category A indicates full-blown AIDS. Category B indicates illnesses and symptoms (e.g., Kaposi's sarcoma) that qualify as an AIDS diagnosis. Category C indicates illnesses and symptoms (e.g., cervical intraepithelial neoplasia) that are attributable to or complicated by HIV infection, but which are not AIDS-defining.

category a, b, c, d, x (drugs)

FDA pregnancy risk categories that indicate risk to a fetus from maternal use of a drug. Category A drugs have not shown a risk in controlled studies. Category B drugs either have not been tested in animals or show adverse effects in animals which have not been confirmed in humans. Category C means that no controlled studies have been done in humans. Category D indicates that there is evidence of human fetal risk, but the benefits of the drug may outweigh the risk. Category X includes drugs which in animal and human studies (or common experience) have been shown to cause fetal abnormalities.

catheter

a flexible tube inserted into a body channel to maintain an opening to the channel. Catheters are commonly used in veins for ongoing drug treatment.

cautery

burning or cutting tissue by means of heat, chemicals or an electric current.

cavitating

creating holes. Used to describe the effect active tuberculosis has on lung tissue.

CBC

abbreviation,  complete blood count. a battery of blood tests, including counts of various cells, hematocrig, and hemoglobin.

CBO

abbreviation,  see community-based organization.

CC

abbreviation,  cubic centimeter, often used as a unit of measurement for drug dosages.

CCR5

abbreviation,  see CKR5.

CD

abbreviation,  see cluster of differentiation.

cd4

a protein embedded in the surface of some T-cells and certain other cells (e.g., macrophages, Langerhans cells, glial cells). HIV invades cells by attaching to their CD4 receptor.

cd4 count

The number of helpter T-lymphocytes in a patients blood, usually expressed as the number of cells per cubic millimeter. When this value drops below 200, the patient has AIDS. Also called t cell count.

cd4/cd8 ratio

the ratio of CD4 cells to CD8 cells. In healthy individuals the CD4/CD8 ratio is about 2.

cd8 (t8)

protein embedded in the surface of killer and suppressor T-lymphocytes. Blood tests that look for suppressor T-lymphocytes are actually looking for this protein.

CDC

abbreviation,  Centers for Disease Control and Prevention -- an agency of the U.S. Department of Health and Human Services, located in Atlanta, Georgia. CDC's mission is to promote health and quality of life by preventing and controlling disease, injury, and disability.

ceiling effect

the phenomenon in which a drug reaches a maximum effect, so that increasing the drug dosage does not increase its effectiveness.

cell

the smallest structural unit of an organism that is capable of independent functioning. A cell consists of a nuclei, cytoplasm, various organelles, and inanimate matter, all surrounded by a semipermeable plasma membrane.

cell antiviral factor

a factor produced by CD8 cells that is hypothesized to block viral infection during the HIV latency period and in long-term nonprogressors. The identity of this factor is not known; possibilities include IL-16 and the chemokines RANTES, MIP-1-alpha and MIP-1-beta. (caf)

cell cycle

the sequences of events a cell goes through in the process of replication. The cycle consists of 4 stages: G1, a resting stage prior to replication; S, in which DNA is synthesized; G2, a "gap" stage; and M, in which mitotic cell division takes place.

cell expansion

an immunomodulating therapy in which cytotoxic T-lymphocytes are removed from the body of an HIV-infected person, treated with IL-2 to induce proliferation, and reinfused into the person in order to strengthen the cell-mediated immune response.

cell line

a specific type of cell that is maintained in vitro for medical and/or research purposes.

cell membrane

the envelope around a cell which encloses the cytoplasm and is responsible for the exchange of materials with the surrounding environment.

cell-associated virus

virus that resides within a host cell. Contrast with cell-free virus.

cell-free virus

virus that exists outside of cells within the bloodstream. Contrast with cell-associated virus.

cell-mediated immunity

part of the immune system responsible for direct attack foreign material without using proteins (antibodies), consists mainly of T-lymphocytes, killer cells, and macrophages.

cellulitis

an inflammation of subcutaneous connective tissue.

centers for disease control and prevention (cdc)

the U.S. federal government agency within the Public Health Service of the Department of Health and Human Services that monitors disease occurrence and develops policies for preventing diseases and maintaining the health of the population.

centi-

prefix, one-hundredth.

cento-

prefix, one hundred times.

central nervous system

A network in the body consisting of the brain, spinal cord, and nerves. (commonly abbreviated CNS)

cephalosporin

a class of antibiotic drugs similar to penicillin.

cerebellum

the lower back part of the brain responsible for functions such as maintaining balance, and coordinating and controlling voluntary muscle movement.

cerebral toxoplasmosis

see toxoplasmic encephalitis.

cerebrospinal

relating to the brain and spinal cord.

cerebrospinal fluid

a clear, nutrient-rich fluid that circulates around and through the brain and around the spinal cord. (csf)

cerebrum

the upper frontal part of the brain responsible for thought and for higher motor functions and sensory processing. The term cerebral is often used to refer to the brain in general.

cervical cancer

Women only. Malignant growth in the narrow lower or outer end of the uterus. In some cases, this is considered an AIDS-defining condition in the United States.

cervical dysplasia

Women only. Abnormal tissue growth in the narrow lower or outer end of the uterus. This can lead to cervical cancer

cervical intraepithelial neoplasia (cin)

abnormal growth of cells of the uterine cervix, suggesting an early stage of cervical cancer. Human papillomavirus (HPV) and HIV infection are associated with an increased risk of CIN. There are 3 grades of severity: CIN I, CIN II and CIN III. A newer classification system divides these 3 classes into 2 categories: low-grade and high-grade squamous intraepithelial lesion (SIL). See also cervical dysplasia, squamous intraepithelial lesion.

cervicitis

inflammation of the uterine cervix.

cervix

the cylindrical, lower part of the uterus leading into the vagina. (adjective cervical)

cesarean section

a delivery procedure that involves making an incision through the abdominal wall to remove an infant from the uterus. (c section)

CFIDS

abbreviation,  chronic fatigue immune dysfunction syndrome. See chronic fatigue syndrome.

CFS

abbreviation,  see chronic fatigue syndrome.

chancre

a red, painless ulcer; a primary sore or lesion that forms at the site of entry of a microorganism (e.g., the spirochete bacterium that causes syphilis).

chancroid

a sexually transmitted disease caused by infection with Haemophilus ducreyi. Chancroid is characterized by soft chancres or ulcers.

cheilitis

inflammation and fissures radiating from the corners of the mouth. Cheilitis may be due to various causes (e.g., nutritional deficiencies, candidiasis). (angular cheilitis)

chemokine

a chemical produced by cells that stimulates the activity of other cells. Certain chemokines are associated with autoimmune disorders, and some (e.g., MIP-1-alpha, MIP-1-beta, RANTES) have been shown to affect the activity of HIV.

chemoprophylaxis

disease prevention using chemicals.

chemotherapy

the chemical treatment of disease, especially cancer.

chi

see qi.

chickenpox

an acute contagious disease caused by the varicella-zoster virus (VZV) and characterized by low-grade fever and a rash of itchy fluid-filled vesicles. Chickenpox typically occurs in children; VZV may reactivate later in life to cause shingles, a painful blistering rash.

chiropractic

a system of treatment based on the manipulation of the spinal vertebrae, the misalignment of which is believed to be responsible for pain and illness.

chlamydia

A bacterial infection that can cause disease. Left untreated it can lead to cancer.

chlamydiasis

an infection, usually sexually transmitted, with the bacteria Chlamydia trachomatis. Chlamydiasis is the most common sexually transmitted disease in the U.S. It may be asymptomatic or include symptoms such as genital inflammation and discharge, pelvic pain and fever. Untreated chlamydiasis may lead to pelvic inflammatory disease (PID) and infertility. (chlamydia)Chlamydia may also cause eye disease (trachoma) and pneumonia.

cholangitis

inflammation of the bile ducts, often characterized by jaundice.

cholecystitis

inflammation of the gall bladder, the organ that stores bile.

cholestasis

obstruction of the flow of bile from the gall bladder.

cholesterol

a substance in animal tissue that is an essential component of cell membranes and nerve fiber insulation. Cholesterol is important for the metabolism and transport of fatty acids and in the production of hormones and Vitamin D. Cholesterol is manufactured by the liver, and is also present in certain foods (e.g., eggs, shellfish). There are 2 types of cholesterol in the blood, high-density (HDL) and low-density (LDL) lipoproteins. Very low cholesterol levels may indicate malnutrition.

chop

a chemotherapeutic regimen for cancer treatment that combines cyclophosphamide, hydroxyldaunomycin (doxorubicin, or Adriamycin), vincristine (Oncovin) and prednisone.

chorion

one of the membranes that encloses the fetus within the uterus.

chorionic gonadotropin

see human chorionic gonadotropin.

chromosome

a structure of compact intertwined molecules of DNA found in the nucleus of cells. Chromosome contain the cell's genetic information. Humans normally have 46 chromosomes.

chronic

adj., continuing, constant, lingering, prolonged.

chronic fatigue syndrome (cfs, chronic fatigue imm

an illness characterized by fatigue, neurological problems, joint and muscle pain, and impairment of the ability to function normally for 6 months or longer. CFS is associated with impaired natural killer cell activity. The cause of CFS is unknown, but the condition may be associated with a virus (e.g., Epstein-Barr virus).

cidofovir

a nucleoside analog drug used to treat refractory cytomegalovirus (CMV) infection and acyclovir-resistant herpes simplex virus. (vistide, hpmpc)

cimetidine (tagamet)

a drug directed against histamine receptors. Cimetidine is used to treat peptic (stomach) ulcers by blocking the secretion of stomach acid, and is under study for the treatment of HIV disease.

cin

see cervical intraepithelial neoplasia.

ciprofloxacin (cipro)

an oral antibiotic used to treat common bacterial infections, and used -- in combination with other drugs -- to treat Mycobacterium avium complex disease in people with AIDS. Side effects may include gastrointestinal distress, seizures and rash.

cirrhosis

a condition in which the liver becomes scarred, fibrous and filled with fat, thus reducing its ability to function. Causes include infection (e.g., hepatitis) and excessive alcohol consumption.

ckr5 (ccr5, cc-ckr5)

a protein found on certain blood cells that serves as a receptor site for chemokines. CKR5 acts as a co-receptor which HIV uses to infect cells. Individuals who lack a functional copy of the gene that makes CKR5 are believed to be non-susceptible to HIV infection.

clade

see subtype.

clarithromycin (biaxin)

a macrolide antibiotic used to treat bacterial infections. Clarithromycin is used as treatment and prophylaxis for Mycobacterium avium complex (MAC). Side effects include nausea, taste changes and abdominal pain.

clindamycin (cleocin)

an antibiotic used as treatment and prophylaxis for toxoplasmosis and treatment of PCP in combination with other drugs.

clinical

relating to the treatment of patients. A clinical observation is based on the observed condition of patients and their symptoms, as distinguished from blood tests or other laboratory findings.

clinical endpoint

see endpoint.

clinical trial

a method for testing an experimental drug. (see also Phase I, Phase II, Phase III)

clinical trial (clinical study)

an organized procedure for determining the effectiveness of a new drug or therapy by administering the agent to participants under strictly controlled conditions. In many clinical trials new agents are tested against older agents or an inactive substance (placebo). The clinical trials process includes Phase I, II and III trials and Phase IV postmarketing evaluation.

clofazimine

a drug used to treat leprosy and Mycobacterium avium complex (MAC) disease.

clone

a group of genetically identical cells or organisms derived from a single common ancestor. Also refers to the process of creating identical cells or organisms. Monoclonal refers to the products (e.g., antibodies) of a single clone.

clotrimazole (mycelex)

an antifungal drug approved as a treatment for candidiasis.

clotting factor

one of several proteins involved in the normal clotting of blood.

cluster differentiation (cd)

a marker protein embedded in the surface of cell membranes or the interior of cells. CD molecules determine which other molecules can bind to a given cell (e.g., the CD4 marker allows HIV to invade certain types of cells).

cmi

see cell-mediated immunity.

cmv

abbreviation,  cytomegalovirus. One disease caused by this virus is CMV retinitis, which can cause blindness if left untreated. CMV disease is an AIDS-defining condition.

cns

abbreviation,  central nervous system.

coagulation

clotting; the transformation of a liquid (e.g., blood) into a solid mass.

cobalamin (vitamin b12)

see vitamin B.

coccidioidomycosis

a fungal disease characterized by fever and localized pulmonary (lung) symptoms. Also called San Joaquin fever. This is considered an AIDS-defining condition in the United States.)

coccidioidomycosis (valley fever)

an uncommon fungal disease acquired by inhaling dust particles containing spores of Coccidioides immitis. The disease is characterized by lesions in the upper respiratory tract and lungs, and may sometimes disseminate to visceral organs, bones, skin and other tissues. Symptoms include cough, fatigue, fever and weight loss.

codon

a sequence of 3 nucleotides or bases that encodes the information for a particular amino acid (the building blocks that make up proteins). Changes in specific codons can confer resistance to certain drugs (e.g., a codon 215 mutation is associated with AZT resistance).

coenzyme q10 (coq10)

a quinone substance that facilitates the production of energy from food and acts as an antioxidant.

cofactor

a substance that activates an enzyme, commonly an inorganic ion, coenzyme, or vitamin. The virus herpes (HSV) is sometimes called an AIDS cofactor because people infected by both the herpes virus and HIV often progress to AIDS faster than people infected only by HIV.

co-factor

a factor (e.g., substance, microorganism, environmental condition) that influences the progression of a disease or the action of a disease-causing agent.

cognitive impairment

Problems with memory and thinking. Can be caused by HIV. Sometimes used to describe a less severe form of dementia.

cohort

a group of individuals in a study who share a demographic, clinical or other statistical characteristic (e.g., age, study site).

colitis

inflammation of the mucous membrane of the colon, which is part of the intestines.

colon

the large intestine, extending from the cecum (where it meets the small intestine) to the rectum.

colonoscopy

examination of the large intestine using a narrow, flexible lighted tube.

colony-stimulating factor (csf)

a cytokine responsible for regulating the production of white blood cells. Types include granulocyte colony-stimulating factor (G-CSF) and granulocyte macrophage colony-stimulating factor (GM-CSF), which are used to relieve neutropenia.

colostrum

breast fluid (produced prior to milk production) that contains large amounts of proteins, calories, immunoglobulins and lymphocytes.

colposcopy (biomicroscopy)

examination of a tissue surface (particularly the uterine cervix) with a low-powered, lighted microscope (colposcope) to identify abnormal cell growth and, if necessary, remove a tissue sample for biopsy.

combination therapy

using 2, 3, or more drugs at the same time. Studies have shown that taking multiple anti-HIV drugs is more potent than taking a single drug.

commensal organism

an organism that normally lives within the body, usually without causing illness.

community advisory board (cab)

a group of community members (e.g., people with HIV/AIDS, care providers, advocates) who provide recommendations regarding clinical research.

community constituency group (ccg)

a group of individuals representing diverse communities affected by HIV/AIDS that advises the ACTG on issues related to clinical research.

community programs for clinical research on aids (

a community-based clinical trials network sponsored by NIAID. CPCRA conducts Phase II and III studies in community settings with a focus on new treatments for opportunistic infections, particularly in underserved populations.

community-based organization (cbo)

a local organization within a community that provides various services to people with HIV/AIDS.

compartment

a separate structural portion (e.g., of the body or of a cell). The term is also used in pharmacology to denote an area of the body where a drug is metabolized, but which may not have a discrete physical boundary.

compassionate use

a classification of an experimental drug (IND) that is made available to seriously ill patients before the drug is approved for general use. Few drugs get this classification. Compassionate use drugs are usually free to the patient.

complement

proteins in the blood that play a part in immune defense against invading organisms. Complement proteins, in conjunction with an antibody-antigen complex, initiate a sequence of events -- the complement cascade -- that results in the destruction of the membrane of the organism or cell under attack.

complementary therapy

an additional treatment or therapy that adds benefit to an existing treatment regimen.

complete blood count

a battery of blood tests, including counts of various cells, hematocrig, and hemoglobin.

complete blood count (cbc)

a screening of the cellular components of the blood, including red blood cell count (including hematocrit and hemoglobin), counts of various types of white blood cells such as granulocytes and T-cells, and platelet count.

compliance

adherence by a patient to a prescribed medical regimen.

compound q

see trichosanthin.

compund q

see trichosanthin.

computed tomography scan (ct scan)

a method of visualizing soft tissues of the body using X-rays. Also known as computed axial tomography or CAT scan.

concomitant

accompanied by or occurring at the same time. Concomitant therapies are those that are used together.

concurrent

occurring at (or, for drugs, taken at) the same time.

condom

a sheath made of latex, polyurethane or animal membrane that is worn over the penis to prevent transmission of semen. Condoms are used to prevent pregnancy; latex and polyurethane condoms protect against the spread of HIV and other sexually transmitted diseases.

condylomata acuminata

genital and/or anal warts caused by infection with a strain of the human papillomavirus (HPV). Warts may appear as tiny white spots or as larger tumors or masses. Condylomata acuminata is typically sexually transmitted and may be particularly aggressive in people with HIV disease (e.g., increased number and size of warts, more frequent recurrence). Warts may be treated with chemicals, surgery or cryotherapy (freezing).

cone biopsy (conization)

removal of a cone-shaped wedge from the bottom of the uterine cervix to remove lesions and to provide a tissue sample for biopsy. See also loop electrosurgical excision procedure.

confidence level (confidence interval)

a statistical measure of the likelihood that an experimental result is "real" and not the result of chance alone. Confidence improves as larger numbers of participants are included in a trial.

confounder

a factor that can influence a trial or experiment, leading to unexpected outcomes that improperly skew the results.

congenital

refers to a disease or condition that is present from the time of birth.

conjunctivitis (pink eye)

inflammation of the conjunctiva, the membrane that covers the eyeball, characterized by redness, watering and itching.

constitutional

not local; affecting the whole body. Constitutional symptoms of HIV disease include fever and night sweats.

contact tracing

a method of finding and informing persons who may have contracted an infectious disease, e.g., through sexual or needle-sharing contact with a person known to be HIV positive.

contagious

an disease that may be transmitted by casual contact from one person to another (e.g., through droplets in the air, on the hands). See also infectious.

contraception

birth control. A contraceptive is an agent or method that prevents conception or successful gestation.

contraindication

any circumstance or condition that makes a method of treatment inadvisable in a particular case.

control arm

a comparison group in a scientific experiment (e.g., a clinical drug trial) that is used to verify experimental results. A control group is not subject to the intervention under (e.g., not given a drug) so that those receiving the intervention and those not receiving it may be compared. Contrast with treatment arm.

controlled trial

a clinical trial in which the group receiving an experimental therapy is compared to a control group that is not given the intervention being studied. In a placebo-controlled trial the control group is given an inactive substance (placebo); in an active control trial the control group is given the best existing proven therapy. Contrast with uncontrolled trial. See also placebo-controlled trial.

convergent therapy

a regimen consisting of several drugs aimed at the same structural or functional target (e.g., a combination of 3 reverse transcriptase inhibitors).

cord blood

blood taken from the remains of the umbilical cord after birth. Cord blood is rich in stem cells.

core

the internal portion of the HIV viral particle. The core proteins, encoded by the gag gene, include the glycoproteins p24 and p17.

co-receptor

a second receptor that enables an organism to infect a cell. In addition to the CD4 receptor on cell surfaces, HIV requires the co-receptor fusin to infect T-cells and the co-receptor CKR5 to infect macrophages.

corroborate

to confirm.

cortex (adjective cortical)

the outer part of an organ (e.g., cerebral cortex, adrenal cortex).

corticosteroid

one of a group of steroid hormones (e.g., prednisone, corticosterone, cortisone, aldosterone) produced by the cortex of the adrenal gland or manufactured synthetically. Corticosteroids are used in the treatment of a variety of conditions; they have anti-inflammatory and immunosuppressive properties.

cortisol

a steroid hormone secreted by the adrenal cortex as part of the body's response to stress. Cortisol promotes the breakdown of body tissues to provide energy and raw materials; high cortisol levels are associated with reduced immune function. Synthetic cortisol (hydrocortisone) is used to reduce inflammation and lessen allergic reactions.

cost recovery

a program under which drug companies are paid to provide a new drug at the expanded access stage, before marketing approval has been granted.

cpcra

abbreviation,  Community Programs for Clinical Research on AIDS. A network of primary care physicians and nurses who work with NIAID staff to design and conduct community-based clinical trials in patients with HIV disease and AIDS.

creatinine

a protein, a normal metabolic waste product found in muscles and blood. The amount of creatinine in the blood or urine tells doctors how well your kidneys are working.

creatinine phosphokinase (cpk)

an enzyme essential for muscle contraction. Blood levels of CPK are typically elevated in muscle diseases (myopathies), and CPK levels can be used to monitor toxicity to the muscles.

crixivan

brand name of indinavir.

crohn's disease

a type of enteritis, or inflammation of the intestines.

cross-immunity

a state in which immunity to one organism serves to protect an individual against a different but related organism (e.g., immunity against cowpox provides immunity against smallpox).

crossover

a trial design in which the therapy given to different arms is switched during the course of the trial (e.g., the arm receiving drug is switched to placebo, and vice-versa).

cross-reactivity

a process by which an antibody responds to an antigen other than that which originally stimulated its production.

cross-resistance

the development of resistance to one agent (e.g., a drug) which also confers resistance to another agent (e.g., a similar drug of the same class).

cross-tolerance

a situation in which tolerance to one drug carries over to another related drug, so that the similar drug has reduced effects.

cryotherapy

treatment procedure involving intense cold (e.g., freezing genital warts).

cryotherapy (cryosurgery)

the use of liquid nitrogen to freeze an abnormal lesion; the lesion typically forms a blister and then heals. Cryotherapy is sometimes used to induce scar formation in order to prevent further spread of abnormal cells (e.g., in cases of cervical dysplasia or retinitis).

cryptococcal meningitis

A fungal infection of the brain and spinal cord. Symptoms include severe headache, dizziness, nausea, weight loss, vision disorders and mental deterioration. Meningitis with headache, blurred vision, confusion, dizziness, nausea, anorexia, depression, agitation or slurred speech are common symptoms.

cryptococcal meningitis (cm)

see cryptococcosis.

cryptococcosis

an infection caused by a yeast-like fungus, typically Cryptococcus neoformans, found in soil and bird feces. A common manifestation is cryptococcal meningitis (CM), an inflammation of the membranes surrounding the brain and spinal cord; cryptococcosis may also become disseminated. Symptoms may include nausea, fever, headache, dizziness, stiff neck, vision and speech difficulties, changes in mental status, increased intracranial pressure and seizures; untreated CM can lead to coma and death. Cryptococcosis may also affect the lungs and may become disseminated, resulting in a red skin rash. Treatments include oral fluconazole and amphotericin B.

cryptosporidiosis

An infection whose main symptom is prolonged diarrhea which leads to weight loss. All treatments for this illness are still experimental.

csf

see cerebrospinal fluid, colony-stimulating factor.

ct scan

see computed tomography scan.

ctl

abbreviation,  cytotoxic T lymphocyte. A cell that can kill foreign cells that were marked for destriction by other immune system cells. (The immune system's hit squat.)

culture

a method of growing a microorganism or living tissue in vitro in a medium that promotes its growth.

cunnilingus

oral sex on a woman; sexual contact between one person's tongue and/or mouth and a woman's vulva, clitoris and/or vagina.

curcumin

an compound present in the spice tumeric. Curcumin has anti-inflammatory and antioxidant properties, and is under study as an anti-HIV therapy.

custodial care

care that provides for daily needs and bodily maintenance (e.g., feeding, hygiene) rather than attempting to provide a cure.

cutaneous

pertaining to the skin.

cyanosis

a dark purplish coloration of the skin and mucous membranes due to deficient oxygen in the blood.

cyclooxygenase

an enzyme involved in oxygen metabolism. Cyclooxygenase is part of the pathway that mediates bodily response to infection and injury (e.g., inflammation and pain) via substances such as histamine and prostaglandins.

cyclospora

an intestinal parasite that can cause severe diarrhea in people with AIDS. A recent outbreak was associated with contaminated North American strawberries.

cyclosporin a

a drug that suppresses the immune system. The drug is commonly used in organ transplant recipients to prevent tissue or organ rejection.

cyst

a stage in the life cycle of certain parasites during which they are enclosed within a protective wall; anti-parasitic drugs often have no effect against cysts. See also oocyst.

cysteine

a sulfur-bearing amino acid that makes up part of the compound glutathione.

cystitis

an inflammation of the urinary bladder.

cyto-

prefix, cell.

cytochrome p450 system

a process that metabolizes drugs and other foreign substances in the liver, by means of the CP450 enzymes.

cytokine

protein produced by some white blood cells (macrophages, monocytes, lymphocytes) used as messangers. Cytokinds produced in the lymph system are also called lymphokinds.

cytology

the study of the structure, function and pathology of cells.

cytolytic

having a destructive effect on cells, causing them to erupt or burst.

cytomegalovirus

abbreviation,  cytomegalovirus. One disease caused by this virus is CMV retinitis, which can cause blindness if left untreated. CMV disease is an AIDS-defining condition. (commonly abbreviated CMV)

cytomegalovirus (cmv, human herpesvirus 5)

a herpesvirus. CMV infection often occurs in healthy individuals without causing symptoms. In immunocompromised individuals (usually at CD4 counts below 50 cells/mm3), CMV may cause serious illness including retinitis (inflammation of the retina), pneumonia, colitis (inflammation of the large bowel) and encephalitis. CMV infection of a pregnant woman may lead to congenital abnormalities in the newborn. CMV may be treated with ganciclovir, foscarnet or cidofovir.

cytopathogenicity

ability to cause disease in cells.

cytopathology

disease, disorders or destruction of cells.

cytopenia

reduced levels of the cellular elements in the blood.

cytoplasm

the gel-like substance that composes cells and lies outside the cell nucleus. The cytoplasm contains numerous structures or organelles (e.g., mitochondria) and component substances.

cytosine (c)

one of the pyrimidine nucleic acid bases that make up nucleotides, the building blocks of DNA and RNA.. The antiviral drug ddI is a nucleoside analog associated with cytosine.

cytotoxic t lymphocyte

A cell that can kill foreign cells that were marked for destriction by other immune system cells. The immune system's hit squat. (also abbreviated CTL)

cytotoxic t-lymphocyte (ctl, t-killer cell)

a type of white blood cell that bears the CD8 surface marker, and targets and kills cells infected with viruses, bacteria, parasites and other microorganisms. The action of CTL is coordinated by CD4 cells via the production of cytokines.

cytotoxicity (adjective cytotoxic)

the quality of being toxic to or killing cells.

cytotoxin

a protein poisonous to certain cells.

cytovene

brand name of ganciclovir. D D4T (STAVUDINE, ZERIT): an antiviral nucleoside analog drug approved for the treatment of HIV disease. D4T inhibits the activity of the reverse transcriptase enzyme needed for HIV replication. Side effects include nausea, peripheral neuropathy and liver toxicity.

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