impetigo A skin infection caused by the staphylococcus or, less often, by the streptococcus bacterium. The first sign of impetigo is a patch of red, itchy skin. Pustules develop on this area, soon forming crusty, yellow-brown sores that can spread to cover entire areas of the face, arms, and other body parts. Most patients are…
imperforate anus See anus, imperforate.
impaction, dental See dental impaction.
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.
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…
immunotherapy See biological therapy.
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.
immunosuppression Suppression of the immune system and its ability to fight infection. Immunosuppression may result from certain diseases, 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 marrow or other organ transplantation, to…
immunology The study of all aspects of the immune system, including its structure and function, disorders of the immune system, blood banking, immunization, and organ transplantation.
immunologist A physician or another degreed professional who is knowledgeable about immunology.
immunohistochemistry A laboratory test to identify, under the microscope, particular chemicals or proteins in tissues or cells by attaching them to specific antibodies which, in turn, are linked to fluorescent dye or enzyme markers for visualization. For example, immunohistochemistry is used by pathologists in the diagnosis of cancers and other conditions.
immunoglobulin M A class of immunoglobulins found in blood and lymph fluid that are the first type of antibody made in response to an infection. Abbreviated IgM. IgM antibodies make up about 5 percent to 10 percent of all the antibodies in the body.