Immunoglobulin Classes in Serological Reactions

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Questions and Answers

What are the three possible formats in which agglutination tests can be performed?

On slides, In tubes, In microtitration plates

What is the difference between active and passive agglutination slide tests?

Active agglutination involves direct agglutination of bacterial antigen with its corresponding antibody, while passive agglutination involves attachment of specific antibody or known antigen to inert particles or cells.

What is the main advantage of slide agglutination tests?

They are rapid and easily performed

Why is it important to check for autoagglutination before adding antiserum in slide agglutination tests?

To prevent false agglutination due to the organism not emulsifying well or the fluid evaporating Signup and view all the answers

What is the role of inert particles or cells in passive agglutination slide tests?

They are used to show that an antigen-antibody reaction has occurred Signup and view all the answers

What is the limitation of slide agglutination tests compared to tube or microtitration techniques?

They are not usually as sensitive Signup and view all the answers

What is an example of an active agglutination slide test?

Slide agglutination of salmonellae, shigellae, or Vibrio cholerae by using specific antibody Signup and view all the answers

Why are slide agglutination tests used to identify bacteria from cultures difficult to standardize and control?

They are difficult to standardize and control Signup and view all the answers

What is the primary phase of agglutination reaction?

Sensitization, where Ab reacts with a single antigenic determinant on the surface of Ag. Signup and view all the answers

What is the secondary phase of agglutination reaction?

Lattice formation, where Ab bridges the gap between particles, dependent on environmental conditions and the relative concentrations of antigen and antibody. Signup and view all the answers

What is an agglutinin?

An antibody that interacts with antigen on the surface of particles to cause their agglutination. Signup and view all the answers

What is an agglutinogen?

An antigen on the surface of particles that react with the antibody known as agglutinin to produce agglutination. Signup and view all the answers

What is the result of the secondary phase of agglutination?

Visible clumping or agglutination of particles. Signup and view all the answers

What is necessary for lattice formation in agglutination?

At least one Fab portion of the antibody must be attached to an antigenic determinant on each of two adjacent particles. Signup and view all the answers

What occurs during stage one of agglutination?

Antibody molecules attach to their corresponding antigenic site on the particle surface, with no visible clumping. Signup and view all the answers

What is the outcome of the interaction between agglutinin and agglutinogen?

Agglutination, or the clumping of particles. Signup and view all the answers

What is the Prozone effect in agglutination tests?

The Prozone effect is when only higher dilutions of a serum with a high antibody titer show agglutination, due to high levels of IgA (blocking antibody), non-specific inhibitory factors, or antibody excess. Signup and view all the answers

What is the purpose of using antihuman globulin in agglutination tests?

To detect the attachment of IgG antibodies to the antigen, which may not cause visible agglutination. Signup and view all the answers

What are the two stages involved in agglutination?

The two stages are sensitization (first stage) and agglutination (second stage). Signup and view all the answers

What factors affect the sensitization stage of agglutination?

Factors affecting sensitization include affinity constant of Ab, temperature, pH, incubation time, and Ag-Ab proportion. Signup and view all the answers

What factors affect the agglutination stage of agglutination?

Factors affecting agglutination include the size and physical properties of Ab molecules, concentration of Ag sites on each cell, and the distance between cells. Signup and view all the answers

What is the main advantage of microtitration agglutination tests?

Microtitration agglutination tests are more sensitive, economical, easier to perform, and give quicker results compared to traditional tube agglutination tests. Signup and view all the answers

What are the types of microtitration agglutination tests?

Types of microtitration agglutination tests include indirect (passive) haemagglutination test (IHA) and haemagglutination inhibition antibody test (HIA). Signup and view all the answers

What is the significance of microtitration agglutination tests in serological diagnosis?

Microtitration agglutination tests are significant in serological diagnosis as they provide a sensitive and efficient means of detecting antibodies or antigens. Signup and view all the answers

Study Notes

Comparative Efficiency of Immunoglobulin Classes

IgG is strong in precipitation and complement fixation, but weak in agglutination
IgM is strong in agglutination and precipitation, but weak in complement fixation
IgA is variable in precipitation and negative in complement fixation

Phases of Agglutination

Primary Phase (Sensitization): Ab reacts with a single antigenic determinant on the surface of Ag
Secondary Phase (Lattice formation): Ab must be able to bridge the gap between particles so that at least one Fab portion is attached to an antigenic determinant on each of two adjacent particles

Agglutination Reaction

Stage 1: Antibody molecules attach to their corresponding antigenic site (epitope) on the red blood cell membrane, but there is no visible clumping
Stage 2: Antibody molecules crosslink RBCs forming a lattice that results in visible clumping or agglutination

Agglutinin and Agglutinogen

An agglutinin is an antibody that interacts with antigen on the surface of particles to cause their agglutination
An agglutinogen is an antigen on the surface of particles that react with the antibody to produce agglutination
Examples of agglutination reactions include Rheumatoid factor latex agglutination, Bacterial latex agglutination, Coombs test, and Blood typing

Agglutination Tests

Can be performed on slides, in tubes, or in microtitration plates
Slide agglutination tests are rapid, easily performed techniques that give a reaction in minutes or even seconds, but may not be as sensitive as tube or microtitration techniques
Active agglutination slide tests involve direct agglutination of bacterial antigen with its corresponding antibody, while passive agglutination slide tests involve attachment of specific antibody or known antigen to inert particles or cells

Factors Affecting Agglutination

First stage (Sensitization): affinity constant of Ab, temperature, pH, incubation time, and Ag-Ab proportion
Second stage (Agglutination): size and physical properties of Ab molecules, concentration of Ag sites on each cell, and distance between cells

Prozone Effect

Occurs when testing a serum with a high antibody titer, resulting in only higher dilutions showing agglutination
Thought to be due to high level of IgA (blocking antibody), non-specific inhibitory factors, or antibody excess
Diluting the serum appropriately can solve this problem

Microtitration Agglutination Tests

Techniques are performed in microtitration plates
More sensitive, more economical, easier to perform, and usually give quicker results than tube agglutination tests
Types of microtitration agglutination tests include indirect (passive) haemagglutination test (IHA) and haemagglutination inhibition antibody test (HIA)

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Description

Compare the efficiency of different immunoglobulin classes (IgG, IgM, IgA) in various serological reactions such as precipitation, agglutination, and complement fixation. Understand the strengths and weaknesses of each class in these reactions.