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Article: Immunization
- Article from:
- World of Microbiology and Immunology
CopyrightCOPYRIGHT 2003 The Gale Group Inc. This material is published under license from the publisher through the Gale Group, Farmington Hills, Michigan. All inquiries regarding rights should be directed to the Gale Group. (Hide copyright information)
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Immunization
When a foreign disease-causing agent (pathogen) enters the body, a protective system known as the
immune system
comes into play. This system consists of a complex network of organs and cells that can recognize the pathogen and mount an immune response against it.
Any substance capable of generating an immune response is called an
antigen
or an immunogen. Antigens are not the foreign
bacteria
or
viruses
themselves; they are substances such as toxins or
enzymes
that are produced by the microorganism. In a typical immune response, certain cells known as the antigen-presenting cells trap the antigen and present it to the immune cells (lymphocytes). The lymphocytes ...