Antigen Antibody Reactions Definition Flashcards
What is antigen antibody reaction
The antigen antibody reaction is a bimolecular association where the antigen and the antibody combine with each other specifically and in an observable manner similar to an enzymes substrate interaction the only difference is that it does not lead to an irreversible alteration either in antigen or antibody
What are the general properties of antigen antibody reaction
Specific
Noncovalent interactions
Strength and firmness of the antigen antibody reaction
-affinity and avidity
Diagnostic uses
Explain specific
Antigen antibody reaction involves specific interaction of epitope of an antigen with the corresponding paratope of its homologous antibody
Exception is the cross reaction which may occur due to sharing of epitopes among different antigen. Evaluate
Cross-reactions can occur when different antigens share similar or identical epitopes, which can lead to the production of antibodies that recognize and bind to multiple antigens. In this case, an antibody generated against one antigen may also recognize and bind to a similar epitope on a different antigen, leading to a cross-reaction.
Noncovalent Interactions
Hydrogen bond
Electrostatic interactions
Van der waals forces
Hydrophobic interactions
Affinity
Actually, affinity refers to the strength of the interaction between a single epitope on the antigen and its corresponding paratope on the antibody, rather than the sum total of non-covalent interactions. Affinity is a measure of how tightly the antigen and antibody bind to each other at a single binding site. It is usually expressed as the dissociation constant (Kd), which is the concentration of antigen at which half of the antibody binding sites are occupied.
Equilibrium dialysis is one method to measure the affinity of the antigen-antibody interaction. In this method, a known concentration of radiolabeled antigen is incubated with a fixed concentration of antibody, and the unbound antigen is separated from the bound antigen by dialysis. The amount of bound antigen is then measured using scintillation counting, and the dissociation constant is calculated from the binding data.
Surface plasmon resonance (SPR) is another method to measure the affinity of the antigen-antibody interaction. In this method, one molecule (e.g. the antibody) is immobilized on a sensor chip, and the other molecule (e.g. the antigen) is flowed over the surface of the chip. As the antigen binds to the immobilized antibody, it changes the refractive index of the solution near the sensor surface, which can be detected as a shift in the angle of the reflected light. The rate and extent of the binding can be analyzed to determine the dissociation constant and other binding parameters.
Both of these methods are widely used to measure the affinity of antigen-antibody interactions and to optimize the design and selection of antibodies for various applications, such as diagnostics, therapeutics, and research tools
Avidity
Avidity is a measure of how strongly a multivalent antibody (an antibody with many binding sites) can stick to a complex antigen (an antigen with multiple parts). It is influenced by the strength of the individual connections between each binding site on the antibody and each part of the antigen (called epitopes).
Because a multivalent antibody can bind to multiple epitopes at once, the total strength of the antibody-antigen interaction is more complex than just the strength of a single connection (which is called affinity). Avidity takes into account the combined strength of all of these connections, and is a better indicator of how well the antibody can bind to the antigen as a whole.
In summary, avidity is a measure of the overall strength of the connection between a multivalent antibody and a complex antigen, taking into account all of the individual connections between each binding site and each part of the antigen
Marracks lattice hypothesis
Marrack’s Lattice Hypothesis is a concept in immunology that explains the phenomenon of antigen-antibody precipitation. According to this hypothesis, the interaction between an antigen and antibody can lead to the formation of a lattice structure, which can further lead to the formation of visible aggregates or precipitates.
The lattice formation occurs when multiple antigen-antibody complexes come together and form a three-dimensional network. This network is stabilized by non-covalent interactions such as hydrogen bonds, electrostatic forces, and van der Waals forces. The lattice structure is formed only when the concentration of the antigen and antibody is optimal and there is sufficient affinity between the two molecules.
In quantitative immunoassays, the Marrack’s Lattice Hypothesis explains the reason behind the requirement of serial dilution of patient serum before testing with a known quantity of antigen. When the serum is diluted, the number of antigen and antibody molecules is reduced, making it easier for the complexes to form and form a lattice structure. If the concentration of the antigen or antibody is too high, the lattice structure may not form, leading to false-negative results.
Overall, the Marrack’s Lattice Hypothesis provides a framework for understanding the principles of antigen-antibody interactions, precipitation reactions, and the limitations of quantitative immunoassays.
What is the double diffusion in one dimension
The double diffusion in one dimension is a type of immunodiffusion test used to detect the presence of antigen and antibody in a sample
How is the Oakley-Fullthorpe procedure related to the Oudin procedure
The Oakley-Fullthorpe procedure is a modification of the Oudin procedure, in which a column of plain agar is placed between the layer of antigen and the layer of gel incorporated with antibody. This modification allows for the detection of closely related antigens and antibodies.
What is the purpose of placing a column of plain agar in the Oakley-Fullthorpe procedure
The purpose of placing a column of plain agar in the Oakley-Fullthorpe procedure is to allow for the detection of the interaction between the antigen and antibody in a specific location. This allows for the visualization of a visible precipitate band.
What happens when the antigen and antibody diffuse towards each other in the Oakley-Fullthorpe procedure
When the antigen and antibody diffuse towards each other in the Oakley-Fullthorpe procedure, they meet at the line where the plain agar column is located. At this line, the formation of a visible precipitate band occurs
What is the significance of the precipitate band formed in the Oakley-Fullthorpe procedure?
The significance of the precipitate band formed in the Oakley-Fullthorpe procedure is that it allows for the detection and differentiation of closely related antigens and antibodies. The position and shape of the band can provide valuable information about the specific antigen and antibody being tested.
How can the Oakley-Fullthorpe procedure be used to differentiate between closely related antigens and antibodies?
The Oakley-Fullthorpe procedure can be used to differentiate between closely related antigens and antibodies by comparing the position and shape of the precipitate band formed in response to different antigens and antibodies
What factors can influence the position and shape of the precipitate band in the Oakley-Fullthorpe procedure?
The position and shape of the precipitate band in the Oakley-Fullthorpe procedure can be influenced by various factors, including the concentration of the antigen and antibody, the temperature of the reaction, and the pH of the agar
