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Questions and Answers
What is the term for the initial force of attraction between a single Fab site on an antibody molecule and a single epitope on the corresponding antigen?
What is the term for the initial force of attraction between a single Fab site on an antibody molecule and a single epitope on the corresponding antigen?
The law of mass action states that free reactants are in equilibrium with bound reactants.
The law of mass action states that free reactants are in equilibrium with bound reactants.
True (A)
What is the name of the phenomenon where excess antibody can lead to a false-negative reaction in an immunoassay?
What is the name of the phenomenon where excess antibody can lead to a false-negative reaction in an immunoassay?
Prozone
The overall strength of antigen-antibody binding, representing the sum of all individual antibody-antigen combining site affinities, is called ______.
The overall strength of antigen-antibody binding, representing the sum of all individual antibody-antigen combining site affinities, is called ______.
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Match the following terms with their corresponding descriptions:
Match the following terms with their corresponding descriptions:
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Which of the following conditions is associated with a high antibody concentration and may lead to a false-negative result?
Which of the following conditions is associated with a high antibody concentration and may lead to a false-negative result?
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The Lattice Hypothesis explains why antigen and antibody must be multivalent in order for precipitation or agglutination to occur.
The Lattice Hypothesis explains why antigen and antibody must be multivalent in order for precipitation or agglutination to occur.
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What is the ideal condition in a clinical laboratory for an antibody to have a high sensitivity?
What is the ideal condition in a clinical laboratory for an antibody to have a high sensitivity?
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The ______ occurs when the number of multivalent sites of antigen and antibody are approximately equal.
The ______ occurs when the number of multivalent sites of antigen and antibody are approximately equal.
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Cross-reactivity can sometimes occur when an antibody reacts with an antigen that is structurally similar to the original antigen that induced antibody production.
Cross-reactivity can sometimes occur when an antibody reacts with an antigen that is structurally similar to the original antigen that induced antibody production.
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Flashcards
Precipitation
Precipitation
Combining soluble antigen with antibody to form insoluble complexes.
Agglutination
Agglutination
Particulate antigens aggregate into larger complexes with specific antibody.
Affinity
Affinity
Initial attraction between a single antibody site and an antigen epitope.
Cross-reactivity
Cross-reactivity
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Avidity
Avidity
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Zone of Equivalence
Zone of Equivalence
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Lattice Hypothesis
Lattice Hypothesis
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Prozone
Prozone
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Postzone
Postzone
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Equilibrium Constant (K)
Equilibrium Constant (K)
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Study Notes
Precipitation and Agglutination Reactions
- Precipitation involves combining soluble antigens and antibodies to form insoluble complexes that are visible.
- Agglutination is the process by which particulate antigens (like cells) aggregate to form larger complexes when a specific antibody is present.
Antigen-Antibody Binding
- Affinity is the initial force of attraction between a single Fab site on an antibody molecule and a single epitope on an antigen.
- The strength of attraction depends on the antibody's specificity for a particular antigen.
- Avidity is the overall strength of antigen-antibody binding, calculated by summing the individual affinities of all antibody-antigen combining sites. Greater numbers of bonds result in higher avidity.
Law of Mass Action
- Antigen-antibody binding is reversible and governed by the law of mass action.
- The law states that free reactants are in equilibrium with bound reactants.
- The equilibrium constant (K) represents the difference in the forward and reverse reaction rates. Higher K values indicate a stronger antigen-antibody complex.
- Ideal clinical conditions for assays involve antibodies with high affinity and avidity.
Precipitation Curve
- Zone of equivalence: The number of antibody and antigen multivalent sites is approximately equal.
- Lattice Hypothesis: Each antibody molecule has at least two binding sites; the antigen must be multivalent.
- Prozone: Antibody excess, leading to a false-negative result. Remedy: Dilute the antibody.
- Postzone: Antigen excess, obscuring antibody presence. Remedy: Repeat test with additional sample after a week.
Precipitation Methods: Light Scatter Techniques
- Turbidimetry measures turbidity (cloudiness) of a solution. A detection device measures the reduction in light intensity caused by the solution.
- Nephelometry measures light scattered at a specific angle as it passes through a suspension. It is more sensitive, with lower detection limits for serum proteins.
- Rate nephelometry measures the instantaneous rate of the increase in light scattering after adding reagent to the solution. The rate is directly related to the antigen concentration.
Precipitation Methods: Passive Immunodiffusion
- Passive immunodiffusion determines antigen-antibody complex precipitation in a gel medium, typically agarose.
- Agarose, a purified high-molecular-weight polysaccharide derived from seaweed, stabilizes diffusion and allows visualization of the precipitin bands that form when antigen and antibody diffuse.
- Radial immunodiffusion: Antigen diffuses radially and creates a ring of precipitate for quantification. There are variations like end-point and kinetic methods.
- Ouchterlony double diffusion: Antigen and antibody diffuse horizontally and vertically in a gel. Different patterns indicate different immunological identities.
Precipitation Methods: Electrophoresis
- Immunoelectrophoresis uses electrophoresis to separate proteins, then cuts a trough in the gel parallel to the separation line to allow for further antibody detection via double diffusion.
- The antibodies in the trough allow precipitin patterns (rockets) to form where specific antigen-antibody combinations take place.
Agglutination Methods
- Agglutination: The visible clumping of particles caused by the combination of antibodies with their corresponding antigens.
- Agglutinins: Antibodies involved in agglutination.
- Common particle types: erythrocytes, bacterial cells, latex particles.
- Early diagnostic tests: Widal test.
Direct Agglutination
- Direct agglutination: The naturally occurring antigens on the particle reacting and clumping with corresponding antibodies.
- Example: ABO blood typing.
- Widal test for typhoid fever.
Passive Agglutination
- Passive agglutination: Employing particles coated with antigens that are not usually on the particle's surface to promote agglutination.
- Example: Latex agglutination tests to detect rheumatoid factor, antibodies, and virus antigens.
Reverse Passive Agglutination
- Reverse passive agglutination: The antibody, rather than the antigen, is attached to a carrier particle to detect antigens in patient samples.
Agglutination Inhibition
- Agglutination inhibition reactions are based on competition for limited antibody combining sites between soluble and particulate antigens, with lack of agglutination being a positive result.
- Common use: Detecting antibodies to viruses such as rubella, influenza, and RSV.
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Description
Test your knowledge on antibody-antigen interactions and the key concepts related to immunoassays. This quiz covers terms such as the initial force of attraction, the law of mass action, and factors influencing detection sensitivity in clinical settings. Challenge yourself to match concepts accurately!
