kit, which contains a prefilled syringe of injectable
epinephrine.
See also BRONCHUS-ASSOCIATED LYMPHOID TISSUE
(BALT); MAST CELL.
angioedema A HYPERSENSITIVITY REACTION(allergic
reaction) that produces swelling and fluid accu-
mulation beneath the surface of the SKIN, similar
in appearance to URTICARIA(hives). Angioedema
occurs in response to HISTAMINErelease and typi-
cally affects the face, especially around the eyes
and lips, and can be life threatening when it is
severe or if it develops in the throat. Swelling in
the form of welts may also occur on the hands
and feet. Hypersensitivity reaction to ingested
allergens is the most common cause of
angioedema.
Difficulty BREATHINGwith angioedema is
a medical emergency that requires
immediate hospital care.The doctor can diagnose angioedema based on
the appearance of the symptoms and the person’s
exposure to an ALLERGEN. Treatment may include
ANTIHISTAMINE MEDICATIONS;CORTICOSTEROID MEDICA-
TIONS; or for severe symptoms, an EPINEPHRINE
injection. Cool cloths applied to the sites of the
angioedema may further ease discomfort. After
the histamine release ends, the body reabsorbs the
fluid. Relief improves as the swelling goes down,
and symptoms are generally gone within three or
four days. Avoiding the allergen prevents the
hypersensitivity reaction and the resulting
angioedema.
There is a form of angioedema, hereditary
angioedema, that is an inherited genetic disorder
and not a hypersensitivity reaction. Though there
is similar swelling beneath the skin, there is no
histamine release.
See also ANAPHYLAXIS; GENETIC DISORDERS; IMMUNE
RESPONSE; LIVING WITH ALLERGIES.
antibody A unique molecule that binds with a
specific ANTIGENso the IMMUNE SYSTEMcan neutral-
ize or destroy the antigen. Antigens are molecular
markers on the surfaces of cells that identify the
cells to the immune system. Antibodies are the
immune system’s infantry, patrolling the BLOOD
and LY M P H circulations and responding to fight
INFECTION when invading pathogens breach the
barriers intended to keep them out of the body.
Every time the immune system encounters new
antigens it crafts new antibodies—a distinct and
unique antibody for each antigen. Though anti-
bodies all derive from IMMUNOGLOBULIN E (IgE),
each kind of antibody binds only with its specific
antigen. The immune system has the capacity to
produce millions of unique antibodies.
B-cell lymphocytes, a type of white blood cell
(LEUKOCYTE), produce antibodies each time the
immune response presents a foreign antigen. Once
sensitized to a specific antigen and programmed to
produce antibodies for it, the B-CELL LYMPHOCYTE
becomes a plasma cell and circulates in the blood
and lymph. Whenever the plasma cell encounters
its antigen, it churns out antibodies and releases
them into the blood and lymph. Thousands to mil-
lions of plasma cells are present in the body for
each antibody the immune response generates.
The antibody response is the foundation of
ANTIBODY-MEDIATED IMMUNITY, also called humoral
immunity, the process by which the immune sys-
tem prevents reinfection by specific pathogens.
Vaccines manipulate antibody-mediated immunity
by introducing weakened pathogens (such as
viruses and BACTERIA) to stimulate B-cell lympho-
cytes to produce antibodies against them. The
blood and lymph circulations then contain the
antibodies though the person has never had the
infection.
Blood tests for the presence of specific antibod-
ies help doctors diagnose numerous health condi-
tions and determine whether a person has
immunity against viral infections such as RUBELLA
(German measles) and infectious mononucleosis.
Antibody testing is also a key step in determining
the match potential between an organ transplant
recipient and the donor organ.
For further discussion of antibodies within the
context of the structures and functions of the
immune system, please see the overview section
“The Immune System and Allergies.”
See also ALLERGY; CELL-MEDIATED IMMUNITY; CELL
STRUCTURE AND FUNCTION; COMPLEMENT CASCADE; GAM-
MAGLOBULIN; HYPERSENSITIVITY REACTION; MONOCLONAL
ANTIBODIES (MABS); MONONUCLEOSIS, INFECTIOUS;
ORGAN TRANSPLANTATION; PATHOGEN; VACCINE; VIRUS.antibody 245