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</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</p> Signup and view all the answers

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

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

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

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

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

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

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

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

    How does the antigen-antibody reaction contribute to immunity?

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

    What defines the agglutinins in an agglutination reaction?

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

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

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

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

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

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

    <p>Epitope</p> Signup and view all the answers

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

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

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

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

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

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

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

    <p>Cholinesterase</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</p> Signup and view all the answers

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

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

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

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

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

    <p>Fluorescein</p> Signup and view all the answers

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

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

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

    <p>Phycoerythrin</p> Signup and view all the answers

    What measurement indicates the effectiveness of antigen detection in ELISA?

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

    What characteristic do antigens and antibodies share in their interaction?

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

    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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