Antigen-Antibody Reaction Quiz
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Questions and Answers

What is the first stage of the antigen-antibody reaction?

  • Visible events like precipitation
  • Destruction of Ag
  • Formation of Ag-Ab complex (correct)
  • Nonspecific binding of antibodies

Which of the following best describes the specificity of an antibody?

  • Antibodies have no specific binding sites
  • Each antibody can react with any pathogen
  • An antibody can bind to multiple antigens
  • An antibody can only bind with one antigenic determinant (correct)

What term describes the complex formed when an antibody binds to a soluble antigen?

  • Antigenic determinant
  • Antigenic site
  • Precipitate
  • Immune complex (correct)

Which stage of the antigen-antibody reaction includes visible events like agglutination?

<p>Visible events stage (A)</p> Signup and view all the answers

What is the role of an antigen in the immune complex?

<p>To act as a specific epitope (B)</p> Signup and view all the answers

What is the result of mixing a specific antigen with its corresponding antibodies?

<p>Clumping of particles (C)</p> Signup and view all the answers

Which example illustrates the specificity of the antigen-antibody reaction?

<p>An antibody produced against kidney antigen reacting only with kidney antigen (C)</p> Signup and view all the answers

In radial immunodiffusion, what happens when Ag or Ab preparations are complex?

<p>Multiple bands form (A)</p> Signup and view all the answers

What does the term 'Ag-Ab reaction' refer to?

<p>The interaction between antigens and antibodies (A)</p> Signup and view all the answers

Which method is used for the rapid determination of agglutinating antibodies?

<p>Slide agglutination (B)</p> Signup and view all the answers

How does the antigen-antibody reaction contribute to immunity?

<p>By identifying and neutralizing specific pathogens (D)</p> Signup and view all the answers

What is the purpose of adding saline in the slide agglutination test?

<p>To create a uniform suspension (B)</p> Signup and view all the answers

What defines the agglutinins in an agglutination reaction?

<p>The antibodies that cause clumping (B)</p> Signup and view all the answers

The presence of which particles in the agglutination test indicates a positive result?

<p>Aggregated particles (A)</p> Signup and view all the answers

What is the main difference between slide agglutination and tube agglutination methods?

<p>Slide agglutination is qualitative; tube is quantitative (B)</p> Signup and view all the answers

What is formed when antigens and antibodies react in a suitable environment?

<p>A precipitate (A)</p> Signup and view all the answers

What is the part of an antigen that is recognized by antibodies called?

<p>Epitope (D)</p> Signup and view all the answers

Which of the following is not a type of antigen-antibody reaction?

<p>Signal Transduction (B)</p> Signup and view all the answers

What occurs during the precipitation reaction in a liquid medium?

<p>An insoluble precipitate of Ag-Ab complex is formed (B)</p> Signup and view all the answers

In the context of antigen-antibody interactions, what is the function of a precipitin?

<p>It is the antibody that causes precipitation (B)</p> Signup and view all the answers

What are the zones identified in a precipitation curve?

<p>Zone of Ag, Zone of equivalence, Zone of Ab (D)</p> Signup and view all the answers

What is the primary purpose of the ELISA method?

<p>To quantify the presence of antigens or antibodies (A)</p> Signup and view all the answers

How is the zone of equivalence in a precipitation reaction formed?

<p>When antigen and antibody concentrations are equal (B)</p> Signup and view all the answers

Which of the following describes the role of Fc receptors in the immune response?

<p>They trigger cellular responses such as phagocytosis (D)</p> Signup and view all the answers

What is the main purpose of diluting serum containing antibodies in the tube agglutination method?

<p>To determine the highest dilution that shows agglutination (A)</p> Signup and view all the answers

In the Widal test, what specific antigen is introduced to estimate typhoid fever?

<p>Salmonella typhi antigen (B)</p> Signup and view all the answers

Which test employs passive agglutination for the diagnosis of rheumatoid arthritis?

<p>Passive agglutination test (C)</p> Signup and view all the answers

What is the main purpose of the Complement Fixation Test?

<p>To form antigen-antibody complexes that fix complement (B)</p> Signup and view all the answers

What is the significance of the agglutination inhibition reaction in pregnancy tests?

<p>It determines the presence of an antigen through visible clumping (A)</p> Signup and view all the answers

What role do complement proteins play in complement fixation tests?

<p>They are responsible for lysis of RBCs or bacteria (D)</p> Signup and view all the answers

Which enzyme is NOT mentioned as being covalently coupled to ligands in ELISA?

<p>Cholinesterase (A)</p> Signup and view all the answers

Which component is important for the passive agglutination test to function effectively?

<p>Carrier particles coated with antigens (B)</p> Signup and view all the answers

In which type of ELISA is the detection of HIV typically performed?

<p>Indirect ELISA (D)</p> Signup and view all the answers

What would be observed in a non-pregnant individual during a pregnancy test using agglutination inhibition?

<p>No visible clumping observed (D)</p> Signup and view all the answers

What temperature is used to incubate the serum and antigen in the Complement Fixation Test?

<p>4°C (C)</p> Signup and view all the answers

What aspect of the immune reaction is altered in the passive agglutination test compared to standard agglutination tests?

<p>The physical nature of the reaction (C)</p> Signup and view all the answers

What happens if the antigen-antibody complex successfully fixes complement?

<p>Lysis of red blood cells occurs (A)</p> Signup and view all the answers

What is a key advantage of ELISA compared to Radioimmunoassay (RIA)?

<p>It does not require the use of radioactive materials (C)</p> Signup and view all the answers

What is the role of microtiter plates in the indirect ELISA technique?

<p>To immobilize the antigen coat (B)</p> Signup and view all the answers

What might indicate a reactive serum in the Complement Fixation Test?

<p>Complete lysis of red blood cells (A)</p> Signup and view all the answers

What is the role of the colored substrate in the ELISA process?

<p>To develop color that indicates the concentration of the antigen (A)</p> Signup and view all the answers

In a competitive ELISA, what happens to the free antibody as the amount of antigen in the sample increases?

<p>It decreases because more antigen competes for binding (D)</p> Signup and view all the answers

Which of the following dyes is most widely used in immunofluorescence procedures?

<p>Fluorescein (A)</p> Signup and view all the answers

What is NOT a chief use of antigen-antibody reactions?

<p>Development of pharmacological treatments (C)</p> Signup and view all the answers

In which technique is the antigen-antibody mixture incubated before adding to a coated well?

<p>Competitive ELISA (A)</p> Signup and view all the answers

Which fluorescent dye has a significantly higher absorption capacity than fluorescein?

<p>Phycoerythrin (A)</p> Signup and view all the answers

What measurement indicates the effectiveness of antigen detection in ELISA?

<p>Intensity of the developed color (A)</p> Signup and view all the answers

What characteristic do antigens and antibodies share in their interaction?

<p>They combine specifically with each other (D)</p> Signup and view all the answers

Flashcards

Antigen-Antibody Reaction

The specific interaction between an antigen and its corresponding antibody, forming an immune complex.

Specificity of Antigen-Antibody Reaction

The ability of an antibody to bind specifically to only one type of antigen determinant (epitope).

Immune Complex

A complex formed when an antibody binds to a soluble antigen. These can be single complexes (antibody bound to a specific epitope) or larger complexes with more antigens and antibodies involved.

Stages of Antigen-Antibody Reaction

The interaction between an antigen and its corresponding antibody forms a complex. This initial reaction is followed by visible events like precipitation or agglutination. Ultimately, the process can lead to inactivation or destruction of the antigen.

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Serological Reactions

Ag-Ab reactions that occur in a laboratory setting, used to detect the presence of specific antigens or antibodies.

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Strength of Antigen-Antibody Reaction

The strength of the binding affinity between an antigen and its corresponding antibody. It depends on factors like the number of antigen determinants and antibody binding sites involved.

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Types of Antigen-Antibody Reactions

Involves the interaction between antigen and antibody, resulting in various visible effects such as precipitation (forming a solid precipitate), agglutination (clumping of cells), or neutralization (inactivation of antigen).

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Applications of Antigen-Antibody Reactions

Ag-Ab reactions can be used for various purposes:

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What is an epitope?

The part of an antigen that binds to an antibody, initiating an immune response.

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What is a paratope?

The region on an antibody that binds to a specific epitope on an antigen.

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What is a precipitation reaction?

A reaction where soluble antigens combine with antibodies to form an insoluble precipitate.

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What is a precipitin?

The antibody that causes precipitation in a precipitation reaction.

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What is a precipitation curve?

A curve plotted that shows the relationship between the amount of precipitate formed and the concentration of antigen added in a precipitation reaction.

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What is Radial Immunodiffusion (Mancini)?

A technique for detecting and quantifying antigens using precipitation reactions in a gel medium.

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What is the zone of equivalence?

When the concentration of both antigen and antibody are optimal, and the precipitation reaction is at its peak.

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What is the zone of antigen excess?

The stage of a precipitation reaction where the concentration of antigen is high, and there is little precipitate formed.

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Radial Immunodiffusion

A technique where antigens and antibodies are allowed to diffuse through an agar matrix and form visible precipitate rings when they meet.

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Double Immunodiffusion

A technique where antigens and antibodies are allowed to diffuse towards each other in an agar matrix, forming a visible precipitate line at the point where they meet.

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Agglutination

The process of clumping together of particles, like cells or bacteria, when they bind to specific antibodies.

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Agglutinins

Antibodies that cause agglutination, specifically binding to antigens on the surface of cells or particles.

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Agglutinogens

Particulate antigens that can be aggregated by agglutinins.

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Slide Agglutination

A rapid diagnostic test where a suspension of particulate antigens is mixed with antiserum on a slide. Agglutination indicates a positive result.

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Tube Agglutination

A standard method for quantitatively measuring antibodies by observing their effect on known antigens in a tube.

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Haemagglutination

The process of using agglutination reactions to identify blood types and determine compatibility for transfusions.

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Tube Agglutination Test

A laboratory technique used to detect the presence of antibodies (Ab) against specific antigens (Ag) in a sample, often serum. It relies on the principle of agglutination, where the antigen and antibody combine to form visible clumps.

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Widal Test

A serological test used for the diagnosis of typhoid fever, where a known amount of Salmonella typhi antigen is mixed with serially diluted patient serum and the highest dilution showing visible agglutination is considered the titre.

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Passive Agglutination

A variation of agglutination tests where a carrier particle, like red blood cells, latex particles or bentonite, is coated with the antigen. When mixed with patient serum containing specific antibody, this leads to agglutination, allowing for a more sensitive detection. This is used in diagnosis of conditions like Rheumatoid arthritis.

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Agglutination Inhibition

This assay is used to detect small quantities of antigens. It involves mixing a known amount of antibody with a sample containing the antigen. The antibody binds to the antigen preventing it from clumping with other carrier particles. The absence of agglutination indicates the presence of the antigen.

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Complement Fixation

A serological test that uses the principle of complement fixation to detect the presence of specific antibodies. Complement proteins bind to the antigen-antibody complex, triggering a cascade of reactions that ultimately lead to lysis of red blood cells. Absence of lysis indicates a positive result.

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Complement Fixation Test

A serological test that detects the presence of antibodies in a serum sample by measuring the ability of the antibody to bind to a specific antigen.

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ELISA (Enzyme-Linked Immunosorbent Assay)

A highly sensitive and widely used technique that employs enzymes to detect the presence of antigens or antibodies in a biological sample.

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Indirect ELISA

A type of ELISA commonly used to detect the presence of antibodies. The antigen is bound to a solid surface (e.g., microtiter plate) and the patient's serum is added.

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Sandwich ELISA

A type of ELISA that is used to detect antigens within a sample. The antibody is immobilized on the plate and the sample is added.

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Enzyme Labeling

A technique used in the development of ELISA. Involves attaching an enzyme (like peroxidase, betagalactosidase, or alkaline phosphatase) to an antibody or antigen.

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ELISA

A type of immunoassay that uses an enzyme-linked antibody to detect the presence of an antigen. Often used to detect antibodies in serum.

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Competitive ELISA

A variation of ELISA where a known amount of antibody is added to a sample. If the antigen is present, it will compete with a coated antigen for the antibody.

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Immunofluorescence

The process of using fluorescent dyes to mark and detect antigens. It works by illuminating the sample with a light source of a specific wavelength.

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Direct Immunofluorescence

A type of immunofluorescence where labeled antibodies are directly added to the sample and the fluorescent signal is measured.

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Indirect Immunofluorescence

A type of immunofluorescence where a secondary antibody, labeled with a fluorescent dye, is used to detect the primary antibody bound to the antigen.

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Immunodeficiency Disease

A condition where the body's immune system is unable to produce enough antibodies.

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Role of Antigen-Antibody Reactions in Immunity

Antigen-Antibody reactions play a vital role in the body's defense system.

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Study Notes

Antigen-Antibody Reactions

  • Antigens and antibodies combine specifically, creating an antigen-antibody reaction (Ag-Ab reaction).
  • This reaction is the basis for humoral immunity (or antibody-mediated immunity).
  • It's also used to detect infectious agents and some non-specific antigens like enzymes.
  • In vitro Ag-Ab reactions are called serological reactions.

Stages of Antigen-Antibody Reactions

  • First stage: Formation of Ag-Ab complexes.
  • Second stage: Visible events like precipitation or agglutination occur.
  • Third stage: Destruction of the antigen or its neutralization.

Salient Features of Antigen-Antibody Reactions

  • Specificity: Antibodies bind to a unique antigen, similar to a lock and key. This prevents cross-reactions.
  • Immune complexes: Formed when antibodies bind to antigens.
  • Binding sites: Epitopes on the antigen and paratopes on the antibody interact.
  • Binding force: Strength of binding between antigen and antibody.

Binding Site of Antigen-Antibody Reactions

  • Epitopes: Specific regions on the antigen recognized by antibodies, B cells, or T cells.
  • Paratopes: Specific regions on antibodies that recognize and bind to epitopes.

Types of Antigen-Antibody Reactions

  • Precipitation: Formation of an insoluble precipitate when soluble antigen reacts with antibody.
  • Agglutination: Clumping of particulate antigens (like cells) by antibodies.
  • Complement fixation: The ability of the antigen-antibody complex to activate components of the complement system.
  • ELISA (Enzyme-Linked Immunosorbent Assay): A sensitive assay to detect antigens or antibodies using enzyme-labeled reagents.
    • Various types of ELISA exist, with different techniques (e.g., Indirect ELISA, Sandwich ELISA, Competitive ELISA.
  • Immunofluorescence: Using fluorescent dyes conjugated to antibodies to visualize antigens.

Precipitation Reaction

  • A soluble antigen reacts with its antibody in the presence of electrolytes and specific pH/temperature to form an insoluble precipitate (Ag-Ab complex).
  • This reaction can occur in liquid or gel media.
  • Plotting the amount of precipitate against increasing antigen concentration results in a precipitation curve showing different zones like antibody excess, equivalence, and antigen excess zones. Specific patterns in gel mediums are used in testing.

Agglutination Reaction

  • Particulate antigens clump together when mixed with antibodies.
  • Two types:
    • Slide agglutination: A rapid method to detect agglutinating antibodies.
    • Tube agglutination: Used for quantitative estimation of antibodies, like measuring antibody levels in serum tests.

Passive Agglutination

  • Antigens are attached to a carrier particle (e.g., RBCs, latex) to increase the sensitivity of the reaction.
  • Used for tests like rheumatoid arthritis diagnosis.

Agglutination Inhibition

  • A highly sensitive assay for detecting small quantities of antigens.
  • An example includes home pregnancy tests.

Complement Fixation

  • Involves the activation of the complement system when an antigen-antibody complex is formed.
  • Used in various serological tests to detect antigens or antibodies in a sample.

Applications of Antigen-Antibody Reactions

  • Blood grouping and cross-matching.
  • Serological diagnosis of infectious diseases (e.g., typhoid, brucellosis).
  • Quantification/measurement of various substances (using immunoassays).
  • Detecting proteins in serum.
  • Diagnosis of immunodeficiency disorders.

Conclusion

  • The antigens and antibodies specifically interact, forming antigen-antibody reactions.
  • These reactions have various applications.

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Antigen-Antibody Reaction PDF

Description

Test your knowledge on the antigen-antibody reaction, including its stages, specificity, and methods of determination. This quiz covers key concepts such as agglutination and the role of antigens in immunity. Perfect for students studying immunology or related fields.

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