Aids Glossary: C-E
Description
This article is from the Health Articles series.
Aids Glossary: C-E
CD4+ T cells: White blood cells that carry a marker on their surface known as "cluster designation 4" (CD4). These cells are the primary target of HIV. Also known as "T-helper" cells, CD4+ T cells help orchestrate the immune response.
CD8+ T cells: White blood cells that carry the "cluster designation 8" (CD8) marker. A subset of these cells are cytotoxic T lymphocytes, or "killer T cells."
Cell-mediated immunity: The immune response in which cells such as cytotoxic T lymphocytes fight infection.
Challenge: In vaccine experiments, the exposure of an immunized animal to the infectious agent.
Clade: a group of related HIV isolates, classified according to the degree of genetic similarity of their envelope proteins. There are currently two groups of HIV-1 isolates, M and O. M has eight clades, A through H, and O may have an equal number of clades. Also called a subtype.
Cohort: Individuals who share one or more characteristics in a research study.
Complement: Blood proteins that play an important role in the immune response. Generally, complement proteins amplify the effects of antibodies.
Control: A way to look at the results seen in clinical trials of experimental vaccines or drugs. One or more groups of patients are given experimental compound(s), while a control group is given either the standard treatment for the disease or an inactive substance.
Correlates of immunity/correlates of protection: The immune responses that protect an individual from a certain disease. The precise identities of the correlates of immunity in HIV are unknown.
Cytokines: Proteins used for communication by cells of the immune system.
Cytoplasm: The living matter within a cell.
Cytotoxic T lymphocytes (CTLs): White blood cells that can kill foreign cells marked for destruction by the immune system. Also known as "natural killer" cells.
Deletion: Elimination of a gene either in nature or in the laboratory.
Domain: A region of a gene or gene product.
Dose-ranging study: A clinical trial in which two or more doses of an agent are tested against each other to determine which dose works best and is least harmful.
Dose-response relationship: The relationship between the dose of some agent, or the extent of exposure, and a physiological response. A dose-response effect means that as the dose increases, so does the effect.
Double-blind study: A clinical trial in which neither the researchers nor the participants know who is taking which drug or vaccine until the trial is over.
DSMB (Data and Safety Monitoring Board): An independent committee composed of clinical research experts who review data while a trial is in progress to ensure that participants are not exposed to undue risk. A DSMB may recommend that a trial be stopped if there are safety concerns or if the trial objectives have been achieved.
Efficacy: The ability of a drug or vaccine to elicit a beneficial clinical effect.
ELISA: Enzyme-linked immunoabsorbent assay. A blood test commonly used to detect the presence of HIV antibodies. A positive ELISA test generally is confirmed by the Western Blot test.
Empirical: Based on experimental data. Not a theory.
Emulsion: A suspension of droplets of a liquid in another liquid. The two liquids do not mix but are suspended within one another.
Enzyme: A protein that accelerates a specific chemical reaction without itself being altered.
Env: A gene of HIV that codes for gp160, the precursor of the envelope proteins gp120 and gp41.
Envelope: Outer surface of a virus, also called a coat.
Epidemiology: The study of the frequency and distribution of disease in human populations.
Epitope: An area of an antigen molecule that stimulates production of specific antibodies, and combines with such antibodies.
Expression system: In HIV vaccine production, cells into which an HIV gene has been inserted to produce desired HIV proteins.
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