Glossary: foreign

In medicine, foreign describes something that comes from outside the body. A foreign substance in the body’s tissues, such as a bacterium or virus, may be recognized by the immune system as not belonging to the body. This causes an immune response. Other foreign substances in the body, such as artificial joints, are designed to not cause an immune response.

The activity of the immune system against foreign substances (antigens).

The complex group of organs and cells that defends the body against infections and other diseases.

Refers to the practices and procedures used for the prevention, treatment, or relief of symptoms of a diseases or abnormal conditions. This term may also refer to a legal drug used for the same purpose.

In medicine, an improvement related to treatment.

In medicine, a very simple microorganism that infects cells and may cause disease. Because viruses can multiply only inside infected cells, they are not considered to be alive.