Immunology: Precipitation Reactions
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Questions and Answers

What characterizes the process of sensitization in delayed hypersensitivity reactions?

  • Presentation of fragmented antigens to B cells.
  • Immediate response upon first exposure to the antigen.
  • Phagocytization of foreign antigens by macrophages. (correct)
  • Release of destructive antibodies during the initial exposure.

    • How does re-exposure to an antigen differ from the initial exposure in delayed hypersensitivity reactions?

  • Memory T cells are activated to release cytokines. (correct)
  • No memory cells respond upon re-exposure.
  • Only T helper cells are involved in the re-exposure reaction.
  • Re-exposure immediately triggers an inflammatory response.

    • What is a common outcome of a positive tuberculin skin test?

  • Absence of any inflammatory response.
  • Formation of antibodies specific to tuberculosis.
  • Immediate swelling at the injection site.
  • Accumulation of T cells and macrophages at the site. (correct)

    • Which mechanism is primarily responsible for transplant rejection?

    <p>Cytotoxic T lymphocytes (CTLs).</p> Signup and view all the answers

    What typically causes allergic contact dermatitis in sensitized individuals?

    <p>Haptens combining with proteins in the skin.</p> Signup and view all the answers

    What is the primary purpose of performing a dilution series in indirect agglutination tests?

    <p>To determine the concentration of antibodies in the serum</p> Signup and view all the answers

    In which situation would you use latex beads in an indirect agglutination test?

    <p>To create a detection system for specific antibodies</p> Signup and view all the answers

    What is the significance of hemagglutination in laboratory diagnostics?

    <p>It involves clumping red blood cells for blood typing and disease diagnosis.</p> Signup and view all the answers

    How does indirect agglutination differ from direct agglutination?

    <p>Indirect agglutination utilizes antibodies attached to particles for detection.</p> Signup and view all the answers

    What role do particles like latex spheres play in the indirect agglutination test?

    <p>They replace the cellular antigens in the testing process.</p> Signup and view all the answers

    Why is visualization of agglutination important in indirect agglutination tests?

    <p>It indicates the presence of antibody-antigen complexes.</p> Signup and view all the answers

    What occurs when a sample contains antibodies specific to the antigens on latex beads?

    <p>The beads will clump together, indicating a positive result.</p> Signup and view all the answers

    What is the main consequence of the degranulation of mast cells and basophils during anaphylaxis?

    <p>Release of leukotrienes and prostaglandins</p> Signup and view all the answers

    What is a key feature of systemic anaphylaxis?

    <p>Narrowing of airway passages</p> Signup and view all the answers

    What role does IgE play in anaphylaxis?

    <p>It facilitates the binding of antigens to mast cells</p> Signup and view all the answers

    What is the primary treatment for anaphylactic shock?

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

    What happens to blood vessels during anaphylaxis?

    <p>They dilate, resulting in decreased blood pressure</p> Signup and view all the answers

    How does localized anaphylaxis differ from systemic anaphylaxis?

    <p>Localized anaphylaxis generally affects limited body regions</p> Signup and view all the answers

    What can cause a systemic reaction in sensitized individuals?

    <p>Even small doses of the antigen</p> Signup and view all the answers

    Which of the following symptoms is NOT typically associated with anaphylaxis?

    <p>Severe abdominal cramping</p> Signup and view all the answers

    What inflammatory mediators are primarily released during anaphylaxis?

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

    What is the primary purpose of neutralization in the context of bacterial infections?

    <p>To block the harmful effects of bacterial exotoxins</p> Signup and view all the answers

    In viral hemagglutination, what role do red blood cells (RBCs) play?

    <p>Acting as a target for viral infection</p> Signup and view all the answers

    What is an antitoxin in the context of neutralization reactions?

    <p>A specific antibody that neutralizes harmful substances</p> Signup and view all the answers

    What does the viral hemagglutination inhibition test specifically measure?

    <p>The presence of antibodies that inhibit viral clumping</p> Signup and view all the answers

    Which of the following viruses is NOT mentioned as causing viral hemagglutination?

    <p>COVID-19</p> Signup and view all the answers

    What is the goal of administering antibodies derived from a patient's serum in the context of influenza?

    <p>To neutralize the influenza virus before it binds to RBCs</p> Signup and view all the answers

    What happens if hemagglutination occurs with a mixture of a virus and red blood cells?

    <p>It confirms the absence of antibodies in the serum</p> Signup and view all the answers

    How is neutralization achieved with respect to viruses that cause hemagglutination?

    <p>By using specific antibodies to block virus binding</p> Signup and view all the answers

    What is the consequence of a patient's serum containing antibodies against a given virus during the hemagglutination test?

    <p>The virus is neutralized and cannot agglutinate RBCs</p> Signup and view all the answers

    What occurs when there is a significant excess of antibody in an immune reaction?

    <p>Formation of complement-fixing complexes</p> Signup and view all the answers

    What is necessary for immune complexes to effectively cause an inflammatory reaction?

    <p>A specific antigen–antibody ratio with slight excess of antigen</p> Signup and view all the answers

    In type IV hypersensitivity reactions, which immune cells are primarily involved?

    <p>T cells and macrophages</p> Signup and view all the answers

    What can repeated introduction of the same antigen cause?

    <p>More serious inflammatory reactions</p> Signup and view all the answers

    What is the role of neutrophils in the immune complex-mediated reaction?

    <p>They release enzymes that cause tissue damage.</p> Signup and view all the answers

    Which statement is true regarding the small soluble complexes formed during an immune response?

    <p>They readily activate complement.</p> Signup and view all the answers

    In immune complex-mediated hypersensitivity, where do the complexes typically become trapped?

    <p>In the basement membrane beneath endothelial cells</p> Signup and view all the answers

    What characterizes delayed hypersensitivity reactions?

    <p>Time requirement for T cells to migrate and accumulate.</p> Signup and view all the answers

    Which immunoglobulin is primarily involved in forming immune complexes in serum?

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

    What happens when there is a significant excess of soluble antigen in an immune reaction?

    <p>Soluble complexes form that do not fix complement or cause inflammation.</p> Signup and view all the answers

    Study Notes

    Precipitation Reactions

    • Precipitation reactions occur when soluble antigens react with IgG or IgM antibodies
    • Initially, small antigen-antibody complexes form
    • Subsequently, larger complexes (lattices) precipitate, forming a visible precipitate in the solution
    • Optimal precipitation occurs when the ratio of antigen to antibody is equivalent
    • Precipitation can be observed as a cloudy line or ring
    • Precipitation testing is used in diagnostic settings

    Precipitation Curves

    • No visible precipitate forms if either antigen or antibody is in excess
    • Maximum precipitate forms in the zone of equivalence (optimal ratio of antigen to antibody)

    Precipitin Ring Test

    • Separate solutions of antigen and antibody are placed adjacent to each other in an agar gel or in a solution
    • Cloudy lines of precipitate form where optimal concentrations meet in the zone of equivalence
    • Test tube method: Antibody solution at the bottom of a small tube; antigen solution carefully layered on top
    • Solutions slowly diffuse, reacting when concentrations are appropriate
    • Visible ring of precipitate in the zone of equivalence

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    Lecture 23: Precipitation and Agglutination Reactions PDF

    Description

    Explore the fascinating world of precipitation reactions in immunology. This quiz covers key concepts such as antigen-antibody interactions, precipitation curves, and the precipitin ring test. Test your knowledge on how these reactions are utilized in diagnostic settings.

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