Glossary
A | B
| C | D | E | F
| G | H | I | J
| K | L | M
| N | O | P | Q
| R | S | T | U
| V | W |
X-Z
A
ACUTE: rapid in onset, aggressive;
short-term initial stage of a disease. Contrast with chronic.
ADHERENCE: refers generally to the ability to follow a prescribed
treatment regimen, including correct dosage, number of doses per day,
and dietary restrictions.
AMINO ACID: an organic compound that is a basic structural unit
of peptides and proteins. There are over 100 amino acids, eight of which
are essential for human metabolism.
ANECDOTAL: refers to evidence based on reports of specific individual
cases rather than controlled, clinical studies.
ANEMIA: the reduced ability of blood to carry oxygen due to
a low hemoglobin level, an abnormality, or a reduced number of red blood
cells. Symptoms include fatigue and weakness.
ANTIBODY (AB, IMMUNOGLOBULIN, IG): an immunoglobulin protein
secreted by activated plasma cells, which evolve from B cells. Antibodies
are present throughout the blood and tissues; they are produced in response
to stimulation by foreign antigens as part of the body’s defense against
disease. Specific antibodies bind to and act upon specific antigens;
the antigen/ antibody reaction forms the basis of humoral (TH2) immunity.
Neutralizing antibodies destroy or inactivate infectious agents, while
enhancing antibodies promote infection.
ANTIGEN: any agent or substance that stimulates an immune response.
Antigens are often foreign microorganisms such as bacteria or viruses,
or the substances they produce.
ANTIRETROVIRAL: an agent that suppresses the activity or replication
of retroviruses such as HIV. Antiretroviral drugs interfere with various
stages of the virus’ life cycle, for example, reverse transcriptase
inhibitors (e.g., AZT, ddI, 3TC) and protease inhibitors (e.g., saquinavir,
ritonavir).
ATROPHY: progressive degeneration, wasting, or decrease in size,
especially the loss of muscle tissue.
AUTOIMMUNE RESPONSE (AUTOIMMUNITY): a condition in which an
individual’s immune system fails to recognize its own biochemical markers
as being “self” and attacks body tissues as if they were foreign matter,
possibly leading to autoimmune diseases such as lupus or rheumatoid
arthritis.
B
BASELINE: an initial or known value (e.g., CD4 cell count, HIV
viral load) against which later measurements can be compared. Bilirubin
levels are measured to gauge the health of the liver.
BONE MARROW: the soft, spongy tissue in the interior of certain
bones (e.g., the long bones of the limbs). Bone marrow contains stem
cells and is the site of blood cell production.
BRANCHED-CHAIN DNA ASSAY (bDNA, QUANTIPLEX HIV RNA ASSAY): a
test that measures the amount of virus (viral load) in plasma or tissue
using a chemical signal, visible as light, that is produced by viral
RNA.
BREAKTHROUGH: a condition that develops despite measures to
prevent it (e.g., PCP that occurs while taking a prophylactic drug).
Also, a rise in viral load after it has fallen due to anti-HIV therapy
(virologic breakthrough)
C
CD4 CELL: a type of white blood cell that carries the CD4 cell
surface receptor and helps the body fight infection. CD4 cells release
cytokines (chemical messengers) that coordinate a broad range of immune
system activities including killer cell activation and antibody production.
See also memory T cell.
CD4 CELL PERCENTAGE: the number of CD4 cells compared with the
number of all lymphocytes. Cell percentage is a more consistent and
reliable measure than absolute cell count. Normal CD4 cell percentages
are usually 30–40% of all lymphocytes.
CESAREAN DELIVERY (CESAREAN SECTION, C SECTION): a delivery
procedure that involves making an incision through the abdominal wall
to permit the removal of an infant from the uterus. CHEMOTHERAPY:
the use of chemicals or drugs to treat disease; the term is typically
used to refer to cancer treatment.
CHROMOSOME: a structure of compact, intertwined molecules of
DNA (deoxyribonucleic acid) found in the nucleus of cells which carry
the cell’s genetic information. Humans normally have 46 chromosomes.
See DNA.
CHRONIC: less intense, slow, persisting over a long period.
Contrast with acute.
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. COFACTOR:
a factor (e.g., substance, microorganism, environmental condition)
that influences the progression of a disease or the action of a disease-causing
agent.
COHORT: a group of individuals in a study who share a demographic,
clinical, or other statistical characteristic (e.g., age, study site).
COLLAGEN: a fibrous protein that makes up connective tissue.
CYTOKINE: an intercellular hormone or chemical messenger protein
(e.g., tumor necrosis factor, interleukin) released by white blood cells
(e.g., macrophages, T cells). Cytokines facilitate communication among
immune system cells and between immune system cells and the rest of
the body. See also interferon.
CYTOMEGALOVIRUS (CMV): a herpesvirus that occurs in healthy
individuals without causing symptoms. In immunocompromised individuals
(usually with CD4 cell counts below 50 cells/mm 3 ), 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.
D
DEMOGRAPHICS: the characteristics of a population (e.g., sex,
race, age, geographic location).
DNA (DEOXYRIBONUCLEIC ACID): a molecule that encodes genetic
information and is found in the nucleus of cells as a twisted double-stranded
chain. The particular sequence of four chemical building blocks (nucleotides)—adenine,
cytosine, guanine, and thymine—that make up a DNA chain determines the
unique genetic code of an individual.
E
ESTROGEN: a female sex hormone; a natural or synthetic substance
(e.g., estradiol, Premarin) that stimulates the development of female
secondary sex characteristics and regulates the reproductive cycle in
women. Estrogens are known to affect the immune system.
F
FUNDUS: the bottom or base of an organ (e.g., eye).
G
GENE: the unit of heredity. A gene contains hereditary information
encoded in the form of DNA and is located at a specific position on
a chromosome in a cell’s nucleus. Genes determine many aspects of anatomy
and physiology by controlling the production of proteins. Each individual
has a unique sequence of genes, or genetic code.
GLUCOSE (BLOOD SUGAR): a form of sugar that is the body’s primary
fuel; glucose broken down from food can be converted into energy or
stored. Abnormally low or high levels of glucose in the blood often
indicate metabolic disturbances (e.g., diabetes).
GLYCEROL: the central structural component of triglycerides
and phospholipids.
H
HAART: highly active antiretroviral therapy, a term for potent
combination anti-HIV treatment that usually includes a protease inhibitor.
HEMATOLOGICAL: see hematology.
HEMATOLOGY: the study of blood and blood-forming tissues.
HEMOGLOBIN (Hb): the red, iron-based pigment in red blood cells
that enables them to transport oxygen. Normal hemoglobin values are
12–15 grams per deciliter (100 milliliters) for women and 14–16 g/dL
for men.
HEPATITIS A (HAV, INFECTIOUS HEPATITIS): an inflammatory viral
disease of the liver with a short incubation period. HAV may be transmitted
by eating contaminated food, by fecal-oral contact, and/or through household
contact. Hepatitis A may be mild to severe; symptoms include fever,
nausea, and jaundice. Two-dose and three-dose anti-HAV vaccines are
available.
HEPATITIS B (HBV, SERUM HEPATITIS): a viral liver disease that
may be acute or chronic, and can be life-threatening. Symptoms include
fever, malaise, fatigue, jaundice, abdominal tenderness, and elevated
liver enzymes. Some individuals are chronic asymptomatic carriers; chronic
hepatitis B may result in liver cirrhosis and/or cancer. HBV can be
transmitted by sexual contact, shared needles, or contaminated blood
products. Interferon alpha is used as a treatment; two three-dose anti-HBV
vaccines are available.
HEPATITIS C (HCV): a contagious viral disease that causes inflammation
of the liver. A chronic carrier state occurs in some individuals and
may result in life-threatening liver damage, cirrhosis, and/or liver
cancer. HCV is spread mainly via contaminated blood products or shared
needles. There is no standard treatment or vaccine.
HERPESVIRUS: a group of viruses that includes herpes simplex
virus type 1 (HSV-1) and 2 (HSV-2), varicella-zoster virus (VZV), Epstein-Barr
virus (EBV), cytomegalovirus (CMV), human herpesvirus types 6 and 7
(HHV-6, HHV-7), and Kaposi’s sarcoma-associated herpesvirus (KSHV).
Herpesviruses may act as opportunistic pathogens and/or cofactors in
HIV pathogenesis.
HORIZONTAL TRANSMISSION: contagion or spread of an infectious
disease from one individual to another within a population. Contrast
with vertical transmission.
HORMONE: a chemical messenger (e.g., adrenaline, testosterone)
involved in the regulation and coordination of cellular and bodily functions.
Hormones may act locally or be secreted into the bloodstream.
HYPERTHYROIDISM: excessive functionality of the thyroid gland
marked by increased metabolic rate, enlargement of the thyroid gland,
rapid heart rate, high blood pressure, and various secondary symptoms.
I
IMMUNOCOMPROMISED: a reduction in immune system function that
results in increased susceptibility to viral, fungal, or bacterial infection.
IMMUNOSUPPRESSION: reduced function of the immune system; a
state in which the immune system defenses have been suppressed, damaged,
or weakened.
INSULIN: a peptide hormone that enables the body to metabolize
and use glucose. Lack of or insensitivity to insulin results in diabetes.
INTERFERON: one of a family of cytokines (messenger proteins)
that play a role in immune response. Interferons are secreted by infected
cells and help protect other cells from infection. The three major classes
are alpha, beta, and gamma interferon. Exogenous interferons (produced
outside the body) are under study as an immunomodulatory therapy for
HIV disease. Side effects of administered interferon include flu-like
symptoms (e.g., fever, aches) and anorexia. Low-dose oral interferon
alpha (Kemron) has not been shown to be effective against HIV disease
in clinical trials.
INTERLEUKIN (IL): a cytokine (chemical messenger) secreted by
immune system blood cells that regulates a range of immune functions.
Types include IL-1, IL-2 (T cell growth factor), IL-10, and IL-12.
INTRACELLULAR: within a cell.
INTRAVENOUS (IV): injected directly into a vein.
J
JAUNDICE: a yellowish discoloration of the skin
and whites of the eyes due to high bilirubin levels resulting from the
breakdown of red blood cells. Jaundice is associated with liver damage
or disease (e.g., hepatitis), gallbladder disease, and excessive destruction
of red blood cells. See also bilirubin.
K
KAPOSI’S SARCOMA (KS): an abnormal or cancerous
proliferation of cells of the blood and/or lymph vessels causing tumors
on the skin, mucous membranes, and/or internal organs. KS typically
appears as purplish or brownish lesions and is associated with a herpesvirus
(KSHV, or HHV-8). It occurs more commonly among HIV positive gay and
bisexual men than among others with HIV disease. KSHV is believed to
be transmitted sexually and through deep (“French”) kissing.
L
LACTIC ACIDOSIS: a buildup of lactic acid (a by-product of carbohydrate
metabolism) in body tissues.
LESION: any abnormal tissue change caused by disease or injury.
LIPID: a fat.
LIPOATROPHY: the depletion of subcutaneous fat stores, especially
in the limbs and cheeks.
LIPODYSTROPHY: a loss of fatty tissue, usually in the limbs
and face. In HIV, the term is commonly used to refer to any type of
body fat redistribution, including accumulations of visceral, abdominal,
and breast adipose tissue. Lipodystrophy may also refer to abnormal
blood lipid and/or glucose metabolism.
LYMPHOCYTE: a type of white blood cell (e.g., T cell, B cell,
natural killer cell) that plays a part in immune defense.
LYMPHOCYTE PROLIFERATION ASSAY (LPA): a test used to measure
the memory of CD4 cells (so-called memory T cells) to antigens or microbes,
such as HIV.
M
MAINTENANCE THERAPY (SECONDARY PROPHYLAXIS): preventive or suppressive
therapy that follows successful initial treatment of an illness. Maintenance
therapy generally continues for the lifetime of the individual to prevent
disease recurrence.
MALAISE: a generalized feeling of illness and discomfort; a
“flu-like” feeling.
MEAN: a statistical measurement of the central tendency, or
average, of a set of values. Contrast with median.
MEDIAN: the number within a series that is preceded and followed
by an equal number of values. Also, the middle value in a distribution,
on either side of which lie an equal number of values. Contrast with
mean.
MEMORY T CELL: a T cell that is specialized to respond to a
specific pathogen and remains in the body after an initial immune response.
Memory T cells respond to a subsequent attack by the same invader in
the future.
MENOPAUSE: the cessation of menstruation. Natural menopause
typically occurs between 45 and 60 years of age; women with HIV may
experience early menopause.
METABOLITE: a product of metabolism, including intermediate
and waste products.
METHADONE: an oral opioid drug used for pain therapy and to
treat opiate (e.g., heroin) addiction. Methadone maintenance therapy
is used to prevent withdrawal symptoms by administering a small dose
of methadone on a regular (e.g., daily) basis.
MOLECULE: a small unit of matter made up of atoms. A molecule
is the smallest unit of a substance that retains its unique characteristics.
MONOTHERAPY: use of a single drug or other therapy.
MULTIVARIATE ANALYSIS: a statistical analysis technique in which
multiple variables are analyzed separately to determine the contribution
made by each variable to an observed result.
N
NEUTROPENIA: an abnormally low number of neutrophils in the
circulating blood, leading to susceptibility to infection.
NEUTROPHIL: the most common type of immune system white blood
cell. Neutrophils are phagocytes that engulf and destroy bacteria and
fungi. The normal count for neutrophils ranges between 3,000 and 7,000;
counts below 500 indicate an increased risk of bacterial infection.
NNRTI: see non-nucleoside reverse transcriptase inhibitor.
NON-NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITOR (NNRTI): a drug
(e.g., nevirapine, delavirdine, efavirenz) that binds with and inhibits
the action of the HIV reverse transcriptase enzyme, thus blocking viral
transcription and replication.
NRTI: see nucleoside reverse transcriptase inhibitor.
NUCLEOSIDE ANALOG: see nucleoside reverse transcriptase inhibitor.
NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITOR (NRTI, also known as
NUCLEOSIDE ANALOG): a compound (e.g., AZT, ddI, 3TC) that suppresses
HIV replication by interfering with the reverse transcriptase enzyme.
O
OPIATE (OPIOID): a class of drugs (e.g., heroin, codeine, methadone)
that are derived from the opium poppy plant, contain opium, or are produced
synthetically and have opium-like effects. Opioid drugs relieve pain,
dull the senses, and induce sleep.
OPPORTUNISTIC INFECTION (OI): a disease caused by a microorganism
that does not normally cause illness in a person with a healthy immune
system, but that may cause serious disease when the immune system is
weakened. Common OIs in HIV positive people include Pneumocystis carinii
pneumonia (PCP), Mycobacterium avium complex (MAC), and cytomegalovirus
(CMV) infection.
OSTEOCALCIN (Bone Gla Protein, BGP): the major noncollagenous
protein of the bone matrix. It is synthesized by osteoblasts. During
bone formation, osteocalcin is partly incorporated into the bone matrix
and partly released into the circulation. Circulation of osteocalcin
has proved to be a specific marker of bone formation.
OSTEOPENIA: a reduction in bone volume to subnormal levels.
OSTEOPOROSIS: atrophy of the bone tissue; a loss of calcium
from the bones. Osteoporosis is influenced by hormonal levels and may
be ameliorated by adequate calcium intake.
P
PALLIATIVE: offering symptomatic relief and comfort care (e.g.,
alleviation of pain) rather than a cure.
PERINATAL: refers to the period around the time of birth.
PHARMACOKINETICS: the action of drugs in the body, including
the processes of absorption, metabolism, transformation, distribution
to tissues, and elimination.
PHOSPHOLIPID: a compound (e.g., lecithin) that contains phosphoric
acid, fatty acids, and nitrogen.
PLACEBO: an inert, inactive substance; a “sugar pill.” Experimental
therapies are compared with a placebo in many clinical trials.
PNEUMOCYSTIS CARINII PNEUMONIA (PCP): a life-threatening opportunistic
type of pneumonia believed to be caused by a protozoan. PCP is a common
infection that can cause severe illness in immunocompromised people
(especially those with CD4 cell counts of fewer than 200 cells/mm 3
); it remains a leading cause of death in people with AIDS. Symptoms
include dry cough, fever, chest tightness, and shortness of breath.
Pneumocystis carinii can also infect other parts of the body. First-line
treatment and primary prophylaxis is TMP-SMX (Bactrim, Septra); other
treatments and prophylaxes include dapsone, pentamidine, and atovaquone.
POLYMERASE CHAIN REACTION (PCR) ASSAY: a highly sensitive test
that can detect small amounts of DNA or RNA (genetic material) in a
blood or tissue sample using an amplification technique that multiplies
the existing DNA/RNA so that it can more easily be detected. PCR assays
are used to determine viral loads in persons infected with HIV.
PRODRUG: an inactive form of a drug that exerts its effects
after metabolic processes within the body convert it to a usable or
active form.
PROLACTIN: a pituitary hormone that stimulates the secretion
of breast milk.
PROPHYLAXIS: therapy that helps to prevent a disease or condition
before it occurs (primary prophylaxis) or recurs (secondary prophylaxis).
PROTEASE INHIBITOR (PI): a drug (e.g., saquinavir, ritonavir,
indinavir) that blocks the action of the HIV protease enzyme, thereby
preventing viral replication. Unlike reverse transcriptase inhibitors,
protease inhibitors can inhibit HIV replication in cells that are already
infected.
S
SEROCONVERSION: the development of antibodies directed against
an antigen; the change in a person’s antibody status from negative to
positive. Vaccine-induced seroconversion is not an infection.
SERUM: the fluid, noncellular portion of blood that remains
after coagulation; lymphatic fluid.
T
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.
THROMBOCYTOPENIA: an abnormally low number of platelets; the
condition may result in abnormal bleeding and bruising. The normal platelet
range is 150,000–450,000 per microliter of blood. Thrombocytopenia may
be controlled by the administration of certain cytokines or by removal
of the spleen.
TRIGLYCERIDE: a combination of glycerol and fatty acid that
circulates in the blood.
V
VERTICAL TRANSMISSION: the conveyance of a pathogen such as
HIV from a mother to a fetus or newborn. Vertical transmission may occur
in utero (in the womb), intrapartum (during birth), or postpartum (via
breast-feeding). Contrast with horizontal transmission.
VIRAL LOAD: the amount of virus in the blood or body tissues.
The presence of HIV RNA indicates that the virus is replicating. Changes
in viral load may be used to gauge drug effectiveness and disease progression.
Viral load is measured using tests such as polymerase chain reaction
(PCR) or branched-chain DNA (bDNA), and is typically expressed as the
number of copies of RNA per milliliter (mL) of blood plasma.
VIRAL REBOUND: an increase in viral load following a previous
decrease due to anti-HIV therapy.
VIREMIA: the presence of virus in the blood.
W
WASTING SYNDROME: a condition characterized by atrophy of lean
body mass and involuntary weight loss of more than 10% of normal body
weight. Other symptoms may include chronic diarrhea, fatigue, weakness,
and fever. Death typically occurs when body weight falls to one-third
of ideal weight, or when body cell mass decreases by 50%.
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last updated 11 October 2001
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