IMMUNOASSAY
IMMUNOGLOBULIN INJECTION
antibodies
are injected into the blood
to provide immediate but short-lived
protection against specific
bacteria
,
vir-
uses
,
or
toxins
.
Active immunization, also
called vaccination, primes the body to
make its own antibodies and confers
longer-lasting immunity.
Routine childhood immunization pro-
grammes exist for diseases such as
diphtheria, pertussis, and tetanus (see
DPT vaccination
),
haemophilus influenza
(Hib), measles, mumps, and rubella (see
MMR vaccination
),
meningitis C, and
poliomyelitis
.
Additional immunizations
before foreign travel may also be neces-
sary (see
travel immunization
).
Most immunizations are given by injec-
tion, and usually have no after effects.
However, some vaccines cause pain and
swelling at the injection site and may
produce a slight fever or flu-like symp-
toms. Some may produce a mild form of
the disease. Very rarely, severe reactions
occur due, for example, to an allergy to
1
of the vaccine's components. Not all
vaccines provide complete protection.
Cholera
and
typhoid fever
vaccinations,
in particular, give only partial protection.
People with
immunodeficiency disor-
ders
, widespread
cancer
, those taking
corticosteroid drugs,
or those who have
previously had a severe reaction to a
vaccine
should
not
be
immunized.
Some vaccines should not be given to
young children or during pregnancy.
immunoassay
A group of laboratory
techniques, which include ELISA (en-
zyme-linked immunosorbent assay) and
radioimmunoassay, that are used in the
diagnosis of infectious diseases and
allergies
,
and in the measurement of
hor-
mone
levels in the blood.
immunodeficiency disorders
Disor-
ders in which there is a failure of the
immune system's
defences to fight infec-
tion and tumours. They may be due to
an inherited or a
congenital
defect or
may be the result of acquired disease.
The result is persistent or recurrent in-
fection, including those with organisms
that would not ordinarily cause disease,
and an undue susceptibility to certain
forms of
cancer
. The infections in people
with immunodeficiency disorders are
sometimes called
opportunistic infections
;
examples include
pneumocystic pneu-
monia
,
fungal infections
, and widespread
herpes simplex
infections.
Congenital or inherited deficiencies can
occur in either of the
2
prongs of the
adaptive immune system: humoral or
cellular. Deficiencies of the humoral sys-
tem include hypogammaglobulinaemia
and agammaglobulinaemia. The former
may cause few or no symptoms, depend-
ing on the severity of the deficiency, but
agammaglobulinaemia can be fatal if
not treated with
immunoglobulin
. Con-
genital deficiencies of T-
lymphocytes
may lead to problems such as persis-
tent and widespread
candidiasis
(thrush).
A combined deficiency of both humoral
and cellular components of the immune
system, called severe combined immuno-
deficiency (SCID), is usually fatal in the
1
st year of life unless treatment can be
given by
bone marrow transplant
.
Acquired immunodeficiency may be
due either to disease processes (such
as infection with
HIV
,
which leads to
AIDS
)
or damage to the immune system
as a result of its suppression by drugs.
Severe malnutrition and many cancers
can also cause immunodeficiency. Mild
immunodeficiency arises through a natu-
ral decline in immune defences with age.
immunoglobulin
A type of protein found
in blood and tissue fluids, also known as
an
antibody
. Such proteins are produced
by B-lymphocytes (a type of white blood
cell), and their function is to bind to
substances in the body that are recog-
nized as foreign
antigens
. This binding is
crucial for the destruction of antigen-
bearing microorganisms. Immunoglob-
ulins also play a key role in
allergies
and
hypersensitivity
reactions.
Immunoglobulin G (IgG) is the major
class of immunoglobulin of the 5 in the
blood (IgA, IgD, IgE, IgG, and IgM). Its
molecule consists of
2
parts:
1
binds to
an antigen; the other binds to other
cells, which then engulf the microor-
ganisms bearing the antigen.
Immunoglobulins can be extracted
from the blood of people who have rec-
overed from certain infectious diseases
and used for passive
immunization
.
immunoglobulin injection
Adminis-
tration of
immunoglobulin
preparations
301
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