Hypersensitivity Reactions Overview
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Questions and Answers

Which of the following correctly defines an allergen?

  • A harmless substance that causes excessive immune response.
  • A substance that triggers a delayed hypersensitivity reaction.
  • An antigen that stimulates an IgG antibody response.
  • An antigen that stimulates an IgE antibody response. (correct)

    • What is Atopy commonly associated with?

  • The development of IgE-mediated antibodies to allergens. (correct)
  • A type of innate immunity response.
  • The transient immune response to infections.
  • The resistance to allergens without any immune response.

    • Which statement accurately describes anaphylaxis?

  • An immune response characterized by a chronic inflammatory condition.
  • A benign allergic response that does not pose significant health risks.
  • A type of allergic reaction that occurs gradually over hours.
  • An immediate and exaggerated systemic allergic condition that requires urgent treatment. (correct)

    • What percentage of the Canadian population is estimated to be affected by Seasonal Allergic Rhinitis?

    <p>20-25%</p> Signup and view all the answers

    What best describes the trend in allergy prevalence in developed countries over the past 30 years?

    <p>Allergies have increased by 2 to 3-fold.</p> Signup and view all the answers

    Which hypersensitivity reaction involves IgE antibodies and can lead to anaphylactic shock?

    <p>Type I hypersensitivity</p> Signup and view all the answers

    In Gell & Coombs classification, which type of hypersensitivity involves antibodies binding to cells or tissues?

    <p>Type II hypersensitivity</p> Signup and view all the answers

    What type of immune response is common to all hypersensitivity reactions?

    <p>Adaptive immune response</p> Signup and view all the answers

    Delayed hypersensitivity reactions are primarily mediated by which type of immune cells?

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

    Which of the following is characteristic of Type III hypersensitivity reactions?

    <p>Immune complexes formed by IgG and soluble antigens</p> Signup and view all the answers

    What is the nature of the antigen in hypersensitivity reactions?

    <p>It is typically a protein, may also include haptens.</p> Signup and view all the answers

    Which of the following hypersensitivity types is most closely associated with allergic asthma?

    <p>Type I hypersensitivity</p> Signup and view all the answers

    Which type of hypersensitivity is also known as delayed-type hypersensitivity (DTH)?

    <p>Type IV hypersensitivity</p> Signup and view all the answers

    What role does memory play in hypersensitivity reactions?

    <p>It allows for a quicker response upon subsequent exposures.</p> Signup and view all the answers

    Which type of antibodies are primarily involved in Type II hypersensitivity reactions?

    <p>Both IgG and IgM antibodies</p> Signup and view all the answers

    What is the primary characteristic of atopy in individuals?

    <p>The propensity to develop IgE-mediated antibodies to allergens</p> Signup and view all the answers

    Which term best describes the acute and severe reaction often resulting from a Type I hypersensitivity?

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

    What factor is primarily responsible for the increase in allergy prevalence in developed countries over the last three decades?

    <p>Improved sanitation and reduced exposure to pathogens</p> Signup and view all the answers

    Which type of immunological response primarily leads to symptoms of allergic asthma?

    <p>IgE-mediated hypersensitivity</p> Signup and view all the answers

    Which allergic condition is characterized by itchy, raised swellings as a response to allergens?

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

    Which type of hypersensitivity is primarily characterized by immune complexes?

    <p>Type III - Immune Complex</p> Signup and view all the answers

    What is the main immunological mechanism involved in Type I hypersensitivity reactions?

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

    Which characteristic is common to all hypersensitivity reactions?

    <p>They involve an adaptive immune response.</p> Signup and view all the answers

    In the context of hypersensitivity, what is a hapten?

    <p>A small molecule that can elicit an immune response only when complexed with a protein</p> Signup and view all the answers

    Which type of hypersensitivity is mediated by T-cells and macrophages?

    <p>Type IV - Delayed hypersensitivity</p> Signup and view all the answers

    What primarily distinguishes Type II hypersensitivity from other types?

    <p>Antibodies binding directly to cell surfaces</p> Signup and view all the answers

    Which statement accurately reflects the sensitization process in hypersensitivity reactions?

    <p>It requires prior exposure to the antigen to initiate a reaction.</p> Signup and view all the answers

    In hypersensitivity reactions, which antigen characteristic is essential?

    <p>Antigen must be a protein or complexed with a protein.</p> Signup and view all the answers

    Which type of hypersensitivity can lead to anaphylactic shock?

    <p>Type I - Allergy</p> Signup and view all the answers

    What is the consequence of a memory response in hypersensitivity reactions?

    <p>It ensures immediate reaction upon re-exposure to the antigen.</p> Signup and view all the answers

    Study Notes

    Hypersensitivity Overview

    • Hypersensitivity reactions occur when the immune system overreacts to a harmless antigen, sometimes causing damage or being fatal.
    • The Gell and Coombs classification categorizes hypersensitivity reactions into four types:
      • Type I: Allergy/Anaphylaxis/Atopy (antibody-mediated).
      • Type II: Antibody-mediated destruction of cells or tissues (antibody-mediated).
      • Type III: Immune complex deposition (antibody-mediated).
      • Type IV: Delayed-type hypersensitivity (cell-mediated).

    Hypersensitivity Type I Reactions

    • Characterized by an immediate response following exposure to an allergen.
    • Involves IgE antibodies, mast cells, and basophils.
    • Allergic asthma is a common example of Type I hypersensitivity.

    Hypersensitivity Type II Reactions

    • Resulting from antibodies (IgG or IgM) binding to antigens on cells or tissues.
    • Mechanisms include complement-mediated cytolysis, antibody-dependent cell-mediated cytotoxicity (ADCC), and activation of anti-receptor antibodies.
    • Examples include transfusion reactions, hemolytic disease of the newborn, and drug-induced reactions.

    Hypersensitivity Type III Reactions

    • Characterized by the formation of immune complexes that deposit in tissues.
    • These complexes activate the complement system and trigger an inflammatory response.
    • Examples include serum sickness, and localized immune complex reactions such as farmer's lung.

    Hypersensitivity Type IV Reactions

    • A delayed-type hypersensitivity resulting from the activation of T cells.
    • Characterized by the recruitment of inflammatory cells (macrophages) and subsequent tissue damage.
    • Examples include the tuberculin skin test, contact dermatitis and some autoimmune diseases.

    Common Features of Hypersensitivity Reactions

    • All involve an adaptive immune response.
    • Sensitization to the antigen is a primary response.
    • A memory response can persist for years (secondary response).
    • Antigens are often proteins, but haptens or drugs may also cause reactions when complexed with proteins.

    Allergic Reaction Phases

    • Sensitization phase involves allergen-specific IgE binding to mast cells/basophils.
    • Activation phase is the re-exposure to the allergen, which triggers mast cell/basophil degranulation and release of inflammatory mediators.
    • Effector phase is the response to inflammatory mediators, resulting in clinical symptoms such as hives, asthma, and anaphylaxis.

    Anaphylaxis

    • A systemic, immediate, and exaggerated allergic reaction that can be life-threatening if not treated promptly.
    • Symptoms and signs include swelling, hives, difficulty breathing, and hypotension.
    • Epinephrine is the crucial treatment for anaphylaxis.

    Clinical Examples

    • Various examples of hypersensitivity reactions are included in the slides, such as allergic asthma, farmer's lung, and hemolytic disease of newborns.

    Immune Complex Clearance

    • Immune complexes are cleared from circulation by various mechanisms including red blood cells (C3b receptors) and macrophages.
    • Deficiencies in complement system components may result in ineffective clearance, leading to immune complex deposition and tissue damage.

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    Related Documents

    Hypersensitivity Reactions PDF

    Description

    Explore the different types of hypersensitivity reactions as classified by Gell and Coombs. This quiz covers Type I to Type IV reactions, including their mechanisms and examples like allergic asthma. Test your knowledge on how the immune system can overreact to harmless antigens.

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