IMMOBILIZATION
IMMUNIZATION
particularly
harmful
in
the
elderly
because it causes muscle wasting and
progressive loss of function.
Total immobility can produce compli-
cations including
bedsores
,
pneumonia
,
or
contractures
.
A common complica-
tion of partial immobility is
oedema
(fluid retention), which causes swelling
of the legs. Rarely, sluggish blood flow
encourages formation of a
thrombus
(abnormal blood clot) in a leg vein.
Regular
physiotherapy
and adequate
nursing care are important for any per-
son who is totally immobile.
immobilization
An orthopaedic term for
techniques used to prevent movement
of joints or displacement of fractured
bones so that the bones can unite prop-
erly (see
fracture
).
immune response
The body's defensive
reaction to microorganisms, cancer cells,
transplanted tissue, and other substances
or materials that are recognized as anti-
genic or “foreign”. The response consists
of the production of cells called
lympho-
cytes
, substances called
antibodies,
or
immunoglobulins
, and other substances
and cells that act to destroy the anti-
genic material. (See also
immune system
.)
immune system
A collection of cells
and proteins that works to protect the
body from
harmful
microorganisms,
such as
bacteria
,
viruses
,
and
fungi
.
It
also plays a role in the control of
cancer
and is responsible for the phenomena
of
allergy
,
hypersensitivity
, and rejection
after
transplant surgery
.
The term innate immunity is given to
the protection that we are born with,
such as the skin and the mucous mem-
branes that line the mouth, nose, throat,
intestines, and vagina. It also includes
antibodies
, or
immunoglobulins
(protec-
tive proteins), that have been passed to
the child from the mother. If microor-
ganisms penetrate these defences, they
encounter “cell-devouring” white blood
cells called phagocytes, and other types
of white cells, such as natural cell-
killing (cytotoxic) cells. Microorganisms
may also meet naturally produced sub-
stances (such as
interferon
) or a group
of blood proteins called the comple-
ment system, which act to destroy the
invading microorganisms.
The 2nd part of the immune system,
adaptive immunity, comes into play
when the body encounters organisms
that overcome the innate defences. The
adaptive
immune
system
responds
specifically to each type of invading
organism, and retains a memory of the
invader so that defences can be rallied
instantly in the future.
The adaptive immune system first must
recognize part of an invading organism
or tumour cell as an antigen (a protein
that is foreign to the body). One of 2
types of response - humoral or cellular -
is then mounted against the antigen.
Humoral immunity is important in the
defence against bacteria. After a complex
recognition process, certain
B-lympho-
cytes
multiply and produce vast numbers
of antibodies that bind to antigens. The
organisms bearing the antigens are
then engulfed by phagocytes. Binding
of antibody and antigen may activate
the complement system, which increas-
es the efficiency of the phagocytes.
Cellular immunity is particularly im-
portant in the defence against viruses,
some types of parasites that hide within
cells, and, possibly, cancer cells. It in-
volves 2 types of T-lymphocyte: helper
cells, which play a role in the recognition
of antigens and activate the killer cells
(the 2nd type of T-lymphocyte), which
destroy the cells that have been invaded.
Disorders of the immune system in-
clude immunodeficiency disorders and
allergy
, in which the immune system
has an inappropriate response to usu-
ally innocuous antigens such as pollen.
In certain circumstances, such as after
tissue transplants,
immunosuppressant
drugs
are used to suppress the immune
system and thus prevent rejection of
the donor tissue as a foreign organism.
immunity
A state of protection against
disease through the activities of the
immune system
. Innate immunity is pre-
sent from birth; acquired (adaptive)
immunity
develops
either
through
exposure to invading microorganisms
or through
immunization
.
immunization
The process of inducing
immunity
as a preventive measure against
infectious diseases
. Immunization may
be active or passive. In the passive form,
300
previous page 298 BMA Illustrated Medical Dictionary read online next page 300 BMA Illustrated Medical Dictionary read online Home Toggle text on/off