Webster's New World Medical Dictionary

immunosuppression
Suppression of the
immune system and its ability to fight infection.
Immunosuppression may result from certain dis-
eases, such as AIDS or lymphoma, or from certain
drugs, such as some of those used to treat cancer.
Immunosuppression may also be deliberately
induced with drugs, as in preparation for bone mar-
row or other organ transplantation, to prevent the
rejection of a transplant. Also known as immunode-
pression.
immunosuppressive agent
A medication that
depresses or halts immune system activity. For
example, immunosuppressive agents may be given
to prevent the body from forming an immune
response to an organ transplant or to treat a disease
that is caused by an overactive immune system, such
as rheumatoid arthritis.
immunotherapy
See 
biological therapy.
immunotherapy, allergy
Stimulation of the
immune system with gradually increasing doses of
the substances to which a person is allergic. The
aim of allergy immunotherapy is to modify or stop
the allergy by reducing the strength of the IgE
response. This form of treatment is very effective for
allergies to pollen, mites, animal dander, and espe-
cially, stinging insects.
impact
To lodge firmly or wedge in. For example,
a molar tooth that is growing up and against an
adjacent tooth is impacting the tooth next to it.
impaction, dental
See 
dental impaction.
imperforate anus
See 
anus, imperforate.
impetigo
A skin infection caused by the staphylo-
coccus or, less often, by the streptococcus bac-
terium. The first sign of impetigo is a patch of red,
itchy skin. Pustules develop on this area, soon form-
ing crusty, yellow-brown sores that can spread to
cover entire areas of the face, arms, and other body