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Questions and Answers
What type of assay is ELISA considered?
What type of assay is ELISA considered?
What is the basis for radioimmunoassay?
What is the basis for radioimmunoassay?
How do fluorochromes function in immunoassays?
How do fluorochromes function in immunoassays?
What is the key feature of direct immunofluorescent assays?
What is the key feature of direct immunofluorescent assays?
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In FPIA, what type of immunoassay is it based on?
In FPIA, what type of immunoassay is it based on?
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What occurs in capture assays during the immune reaction?
What occurs in capture assays during the immune reaction?
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Study Notes
Labeled Immunoassays
- Measure small or low concentrations of antigens and antibodies
- Use various labeling techniques, including:
- Radioactivity
- Enzymes
- Chemiluminescence
- Fluorescence
Types of Immunoassays
- Competitive
- Noncompetitive
- Heterogenous (requiring separation)
- Homogenous
Antibody Requirements
- Must be specific to the antigen in question
- Must have a high affinity for the antigen
Radioimmunoassay
- Based on competition between labeled and unlabeled antigen for a limited number of antibody-binding sites
Noncompetitive Indirect Enzyme Immunoassays (e.g., ELISA)
- Antigen is bound to the solid phase
- Antibody is detected
- A second enzyme-labeled antibody is added after binding occurs
Capture Assays
- Antibody is bound to the solid phase
- Any patient antigen is allowed to bind or be captured
- A second labeled antibody is added that binds to patient antigen, forming a "sandwich"
Fluorochromes
- Fluorescent compounds that absorb energy from an incident light source and convert it to light of a longer wavelength
Immunofluorescent Assays
- Direct immunofluorescent assays:
- Antigen detection through a specific antibody labeled with a fluorescent tag
- Indirect immunofluorescent assays:
- Original antibody is unlabeled
- Incubation with antigen is followed by addition of a second fluorescent-labeled anti-immunoglobulin that detects antigen–antibody complexes
FPIA (Fluorescent Polarization Immunoassay)
- A type of homogeneous fluorescent immunoassay
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Description
Test your knowledge on labeled immunoassays, including techniques such as radioactivity, enzymes, chemiluminescence, and fluorescence. Explore the major types of immunoassays, competitive and noncompetitive, as well as heterogenous and homogenous immunoassays. Understand the importance of specific antibodies with high affinity for antigens.
