(antibodies) to prevent or treat infectious
diseases. Such preparations, also known
as immune globulin or gammaglobulin,
work by passing on antibodies obtained
from the blood of people who have pre-
viously been exposed to these diseases.
The main use of these injections is to
prevent infectious diseases, such as
chickenpox, in people exposed to infec-
tion who are not already immune or are
at special risk (during cancer treatment,
for example).They are also given regu-
larly for immunodeficiency disorders. Side
effects include rash, fever, and pain and
tenderness at the injection site.
immunologyThe discipline concerned
with the immune system.Immunologists
study the immune system’s functioning
and investigate and treat immune system
disorders, including allergies, autoim-
mune disorders, and immunodeficiency
disorderssuch as AIDS. Immunologists
are also concerned with finding ways in
which the immune system can be stim-
ulated to provide immunity. In addition,
they play a role in transplant surgery,
looking preoperatively for a good match
between recipient and donor organ, and
suppressing the recipient’s immune sys-
tem after transplantation to minimize
the chances of organ rejection.
immunostimulant drugsA group of
drugs that increase the efficiency of the
body’s immune system. Immunostimulant
drugs include vaccines, interferonand
aldesleukin (interleukin-2). Interferon is
used to treat persistent viral infections,
such as hepatitis C, and some types of
multiple sclerosis. Aldesleukin is used in
the treatment of some types of cancer.
immunosuppressant drugsA group
of drugs that reduce the activity of the
immune system. They include azath-
ioprine, ciclosporin, cyclophosphamide,
methotrexate, and prednisolone. Immu-
nosuppressants are given to prevent
rejection after transplant surgeryand to
slow the progress of autoimmune dis-
orderssuch as rheumatoid arthritisand
systemic lupus erythematosus.
The drugs work by suppressing the pro-
duction and activity of white blood cells
called lymphocytes. Side effects vary, but
all the drugs increase the risk of infection
and of the development of certain cancers.immunotherapyStimulation of the im-
mune systemas a treatment for cancer.
The term is also used to describe hypo-
sensitizationtreatment for allergy. One
type of immunotherapy used in the treat-
ment of cancer uses immunostimulant
drugs. More recently, monoclonal anti-
bodies (see antibody, monoclonal)
directed against tumours have been
produced artificially by genetic engi-
neering. Interferonor chemical poisons
can be linked to these antibodies to
increase their ability to destroy tumour
cells without damaging normal cells.
impaction, dentalFailure of a tooth to
emerge completely from the gum. It may
occur because of overcrowdingor when
a tooth grows in the wrong direction.
Impacted wisdom teeth are common,
and, if symptomless, may not need to
be removed. In some cases, however,
symptoms necessitate their removal.
impedance audiometryA hearing test
used to investigate the middle ear in
cases of conductive deafness.
imperforateWithout an opening. The
term is used to describe a body struc-
ture, such as the hymenor anus (see
anus, imperforate), in which a normal
perforation is lacking.
impetigoA highly contagious skin infec-
tion, common in children, that usually
occurs around the nose and mouth. It is
caused by bacteria (usually staphylo-
cocci) entering areas of broken skin. The
skin reddens and small, fluid-filled blis-
ters appear. The blisters tend to burst,
leaving moist, weeping areas that dry to
leave honey-coloured crusts. In severe
cases, there may be swelling of the lymph
nodesin the face or neck and fever.
Topicalantibiotic drugscan be used,
but if the condition is widespreadoralIMMUNOLOGY IMPETIGOI
IMPETIGO