Antigen-Antibody Reactions Overview

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Questions and Answers

What is formed when antibodies bind to antigens?

  • Toxins
  • Carrier proteins
  • Immunological complex (correct)
  • Electrolytic solution

What term describes the interaction between an antigen and an antibody?

  • Agglutination
  • Antigen-antibody reaction (correct)
  • Immunology
  • Serological response

Which of the following correctly describes precipitin?

  • The antibody that causes precipitation (correct)
  • A stable virus
  • An electrolyte
  • A type of antigen

What is the prerequisite for haptens to cause an immunological response?

<p>They require carrier proteins. (C)</p> Signup and view all the answers

What environment is necessary for the precipitation reaction to occur?

<p>Specific pH and temperature with an electrolyte (D)</p> Signup and view all the answers

What defines immunogens?

<p>They cause a sequence of immunological responses. (B)</p> Signup and view all the answers

Which statement is true regarding the Ag-Ab reaction?

<p>It serves as the foundation for humoral immunity. (C)</p> Signup and view all the answers

What characterizes the agglutination process?

<p>It combines antibodies and antigens. (D)</p> Signup and view all the answers

What is formed when a specific antigen combines with its antibody in the presence of electrolytes?

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

What is the purpose of the control tube in agglutination tests?

<p>To ensure the test is run with untreated serum (A)</p> Signup and view all the answers

Which component is essential for the lysis of red blood cells in complement fixation tests?

<p>Complement proteins (C)</p> Signup and view all the answers

What type of light does fluorescein absorb to produce fluorescence?

<p>Blue light (B)</p> Signup and view all the answers

In an indirect ELISA, what is the role of the secondary antibody?

<p>To estimate the amount of primary antibody (C)</p> Signup and view all the answers

Which of the following enzymes is NOT commonly associated with ELISA?

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

What type of interaction results in the antigen-antibody reaction?

<p>Specific interactions (C)</p> Signup and view all the answers

What characteristic makes phycoerythrin an effective label for immunofluorescence?

<p>Strong red fluorescence emission (D)</p> Signup and view all the answers

What is the significance of the titre in agglutination tests?

<p>It quantifies the highest dilution of antiserum (A)</p> Signup and view all the answers

What is a key difference between single diffusion and double diffusion methods?

<p>Complexity of setup (B)</p> Signup and view all the answers

Flashcards

Antigens

Foreign substances that trigger an immune response in the body. They can be molecules, proteins, or even parts of viruses or bacteria.

Antibodies

Proteins produced by the immune system in response to antigens. They specifically bind to antigens to neutralize them.

Antigen-Antibody Reaction

The interaction between an antigen and its specific antibody, leading to formation of an antigen-antibody complex.

Precipitation Reaction

A specific type of antigen-antibody reaction where soluble antigens and their antibodies combine to form a visible precipitate.

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Haptens

Substances that are too small to trigger an immune response on their own but can do so when attached to a carrier protein.

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Serological Reactions

Antigen-Antibody interactions that occur in a test tube, outside the living organism.

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Agglutination

Antigen-antibody reactions leading to the clumping together of particles such as bacteria or red blood cells.

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Antibody Specificity

The ability of an antibody to bind with a specific antigen, determined by the antibody's structure.

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Agglutinogens

The particles in an agglutination reaction that are clumped together by antibodies.

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Agglutinins

The antibodies in serum that cause agglutination by binding to agglutinogens.

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Agglutination Test

A test used to determine the presence of specific antibodies in a sample by measuring the amount of agglutination.

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Complement

A protein complex that helps antibodies destroy pathogens by activating lysis (cell breakdown) of the target cell.

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Complement Fixation Test

A test that uses the ability of antigens and antibodies to bind complement to detect the presence of antibodies or antigens.

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Immunofluorescence

A technique that uses fluorescent dyes attached to antibodies to detect and visualize antigens in cells or tissues.

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Fluorescein

A commonly used fluorescent dye that absorbs blue light and emits yellow-green fluorescence.

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ELISA (Enzyme-Linked Immunosorbent Assay)

A technique that uses enzymes attached to antibodies to detect and quantify antigens or antibodies in a sample.

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Direct ELISA

A type of ELISA where known antigens are coated on a plate and the amount of antibody in a sample is measured by how strongly it binds to the antigens.

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Study Notes

Antigen-Antibody Reactions: Types and Processes

  • Antigen-antibody reactions are specific interactions between antibodies and antigens, crucial for the body's immune defense.
  • Agglutination, precipitation, complement fixation, immunofluorescence, and ELISA are types of these reactions.

Precipitation Reactions

  • Soluble antigens combine with antibodies in the presence of electrolytes to form an insoluble precipitate called "precipitin."
  • This reaction happens in liquid or gel mediums.
  • Multiple bands might form in complex antigen or antibody preparations, with techniques like single diffusion and double diffusion used.

Agglutination Reactions

  • Agglutination involves the clumping of particulate antigens when combined with their specific antibodies.
  • The resulting clumps are called agglutinins.
  • Agglutinogens are the name for particulate antigens.
  • Carrier particles (like RBCs, latex, or bentonite) can be used to enhance sensitivity.
  • Agglutination titers indicate the antibody's concentration.

Complement Fixation

  • The complement system, a group of proteins, is pivotal for destroying pathogens.
  • Complement proteins attach to antibodies within the antigen-antibody complex, triggering a series of reactions for cell lysis.
  • Complement fixation tests are used to determine the presence of specific antibodies.

Immunofluorescence

  • Fluorescent dyes, like fluorescein and phycoerythrin, are used to detect antigens by binding to antibodies labeled with these dyes.
  • The dyes emit light under UV radiation for visualization.
  • Coons and colleagues developed this technique in 1942.

ELISA (Enzyme-Linked Immunosorbent Assay)

  • ELISA uses enzyme-labeled antibodies to detect antigens or antibodies in a sample.
  • It's a more convenient, sensitive, affordable, and safer alternative compared to radioimmunoassay.
  • Various enzymes like peroxidase, beta-galactosidase, and alkaline phosphatase are used.
  • Three types of ELISA exist: direct, indirect, and sandwich.
  • Colour intensity in ELISA correlates with antigen concentration in the sample.

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