learning_immunoassay_01 - Chapter 1 Introduction to...

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Introduction to Immunoassays 1 Chapter Immunoassay: Antibodies, Antigens and Analytes Defined Antibodies and Antigens An antibody is a protein that is produced by the body in response to an “invading” (foreign) substance 1 . Antibodies are produced as part of the body’s immune response to protect itself. For instance, some immunoassays test for the presence of antibodies to cancer molecules. Thus, if the antibodies are present, it means invading cancer cells are, too. An antigen is the substance that the body is trying to “fight off” (eliminate or reduce) by mount- ing an immune response. Some immunoassays test for antigens directly, rather than looking for the antibodies. In a test to measure the concentration of a therapeutic drug, for example, the drug is the antigen that binds to the antibody. An analyte is anything measured by a laboratory test. In immunoassay testing, the analyte may be either an antibody, or an antigen. Introduction An immunoassay is a test that uses antibody and antigen complexes as a means of generating a measurable result. An antibody:antigen complex is also known as an immuno-complex. “Immuno” refers to an immune response that causes the body to generate antibodies, and “assay” refers to a test. Thus, an immunoassay is a test that utilizes immunocomplexing when antibodies and antigens are brought together. Immunoassays are different from other types of laboratory tests, such as colorimetric tests, because they use antibody:antigen complexes to generate a signal that can be measured. In contrast, most routine clinical chemistry tests utilize chemical reactions between the reagent (a solution of chemicals or other agents) and patient sample to generate a test result. Learning Objectives After completion of this chapter, you will be able to: define immunoassay describe the structure and preparation of antibodies define four categories of immunoassay methodology (competitive and noncompetitive, and homogeneous and heterogeneous) 1 An exception is the case of auto-immune diseases, where the body produces antibodies to naturally occurring pro- teins rather than foreign substances.
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Preparation of Polyclonal and Monoclonal Antibodies Antibody reagents are developed from either polyclonal or monoclonal antibodies. Polyclonal antiserum (serum from blood containing the desired antibodies) is generated in animals, most commonly sheep, rabbits, or goats. The animals produce the antiserum - just as a human would - as a defense mechanism when exposed to an anti- gen. Antiserum contains a mixture of antibodies, each of which may bind to different antigen binding sites, or epi- topes. The process of making an antiserum begins by injecting a solution that contains the antigen of interest into an animal. This antigen of interest is sometimes called an immunogen, because it can stimulate an immune response. Over time, and in some cases with multiple injections, the immune system of the animal produces antibodies to the antigen that was injected. Blood is collected from the animal, and serum is isolated from the
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This note was uploaded on 04/24/2008 for the course ENGR 213 taught by Professor Clague during the Winter '08 term at Cal Poly.

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learning_immunoassay_01 - Chapter 1 Introduction to...

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