Immunology Reactions and Testing

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Questions and Answers

What is true about all Ag-Ab binding?

All Ag-Ab binding occurs on a fixed surface.

All Ag-Ab binding is temperature-dependent.

All Ag-Ab binding is reversible. (correct)

All Ag-Ab binding is irreversible.

Which method is considered the least sensitive for detecting antigen-antibody reactions?

Immunofluorescence

Radioimmunoassay

Chemiluminescent immunoassay

Agglutination (correct)

In the context of secondary reactions, what is meant by multivalent antigens?

Antigens that can bind to multiple antibody molecules or types. (correct)

Antigens that form irreversible bonds with antibodies.

Antigens that are only detected through immunofluorescence.

Antigens that bind with a single antibody with high affinity.

What is indicated by a higher value of the equilibrium constant (KA)?

More antigen-antibody complexes formed. Signup and view all the answers

Which characteristic best describes the process of serial dilution?

Each dilution results in a fixed change in concentration. Signup and view all the answers

Which reaction method usually requires special equipment and is more time-consuming?

Complement fixation test Signup and view all the answers

What is a common issue associated with tertiary reactions in antigen-antibody interactions?

They frequently involve multivalent antigens. Signup and view all the answers

How does increasing avidity in Ag-Ab complexes affect their stability?

Stability increases, resulting in lower K2 values and higher K1 values. Signup and view all the answers

Which statement best describes the principle behind the Fahey-McKelvey RID method?

The diameter of the precipitation ring relates directly to the antigen concentration. Signup and view all the answers

What occurs during the second phase of double diffusion when an antigen is applied to a well in the gel?

Antigen begins to diffuse out from the well. Signup and view all the answers

What distinguishes immunoelectrophoresis from other RID methods?

It combines both electrophoresis and double diffusion. Signup and view all the answers

In the context of the Mancini RID method, what is the significance of the incubation time?

It influences the size of the precipitation arc. Signup and view all the answers

What is the role of the standard curve in fluid-phase precipitation methods?

To quantify an unknown concentration of antigen. Signup and view all the answers

In the fluid-phase precipitation technique, what characteristic is measured to assess concentration levels?

Diameter of the formed precipitate ring. Signup and view all the answers

Which component is cut into the gel in the immunoelectrophoresis process?

A trough. Signup and view all the answers

What phenomenon is observed when antigen and antibody reach the equivalence point in double diffusion?

Formation of a precipitation arc. Signup and view all the answers

What is the main characteristic of the precipitation that occurs in lethal dose tests?

It involves a narrow range of neutralizing antibodies. Signup and view all the answers

In vivo toxin neutralization tests primarily assess which of the following?

The susceptibility of the organism to the toxin Signup and view all the answers

What is the primary application of the Complement Fixation Test?

To detect antibodies applicable only to IgM Signup and view all the answers

Which interpretation indicates susceptibility to Scarlet fever in Dick's test?

Redness observed with the toxin Signup and view all the answers

What is a common limitation of the Complement Fixation Test as mentioned?

It has been largely replaced by simpler methods. Signup and view all the answers

Which test assesses susceptibility to C. diphtheriae?

Schick's test Signup and view all the answers

What is indicated by a negative result in the Complement Fixation Test?

Lysis of sensitized red blood cells occurred Signup and view all the answers

What does the blanching phenomenon during the Schultz-Charlton reaction indicate?

Susceptibility to Scarlet fever Signup and view all the answers

Study Notes

Immunological Reactions and Testing

Immunological tests are complex, often requiring special equipment and being costly.
Two major types of reactions: primary, secondary, and tertiary.
Primary Tests: More sensitive, includes techniques like immunofluorescence and radioimmunoassay.
Secondary Reactions: Involve multivalent antigens resulting in cross-linking and larger detectable complexes.
Avidity: Increased binding strength reduces dissociation of antibody-antigen complexes, affecting K1 and K2 values.

Serial Dilutions

Serial dilutions decrease concentration at each step uniformly.
Critical in clinical labs to identify dilution factors for accurate testing.
They are multiplicative in nature, crucial for interpreting immune responses.

In Vivo Toxin Neutralization Tests

Dick’s Test: Assesses susceptibility to Scarlet Fever; redness indicates susceptibility.
Schultz-Charlton Reaction: Positive if rashes blanch with antitoxin; diagnostic for Scarlet Fever.
Schick’s Test: Assesses susceptibility to C. diphtheriae.

Complement Fixation Test

Detects antibodies in patient sera, specifically for IgM.
Process involves adding patient serum, reagent antigen, then complement, and sensitized RBCs.
Results: Lysis indicates absence of antibodies; no lysis suggests presence.

Fluid-phase Precipitation

A modification of single-diffusion technique using turbidimetry and nephelometry.
Double Diffusion (Ouchterlony Technique): Antigen diffuses from a well in the gel leading to precipitate formation at equivalence zones.

Immunoelectrophoresis (IEP)

Combining electrophoresis with double diffusion for identifying proteins.
Useful in detecting free light chain proteins and classifying immunoglobulins.

Principal RID Methods

Fahey-McKelvey RID: Kinetic approach with 18-hour incubation; measures ring diameter against log antigen concentration.
Mancini RID: Endpoint method requiring longer incubation; compares precipitation ring size and intensity to normal controls.

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Description

Explore the complex world of immunological reactions and testing methods. This quiz covers primary and secondary tests, the importance of avidity, and serial dilutions for accurate results. Additionally, it delves into in vivo toxin neutralization tests and their significance.