Hypersensitivity Reactions Overview
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Questions and Answers

What type of hypersensitivity reaction is mediated by IgE antibodies?

  • Type I (correct)
  • Type II
  • Type III
  • Type IV

    • Which of the following is NOT a result of a Type I hypersensitivity reaction?

  • Hay fever
  • Bronchial asthma
  • Anaphylactic shock
  • Autoimmune disease (correct)

    • Which statement correctly describes the mediators involved in hypersensitivity reactions?

  • Type II hypersensitivity is the only type that causes anaphylactic shock.
  • Type III hypersensitivity is exclusively cell mediated.
  • Type IV hypersensitivity does not involve antibodies. (correct)
  • Type I hypersensitivity is primarily caused by IgM antibodies.

    • What occurs during the first exposure to an allergen in a Type I hypersensitivity reaction?

    <p>Formation of IgE antibodies begins.</p> Signup and view all the answers

    What mechanism leads to the release of mediators in a Type I hypersensitivity reaction upon re-exposure to an allergen?

    <p>Cross-linking of IgE antibodies on mast cells</p> Signup and view all the answers

    Which of the following statements correctly identifies a role of cytokines produced by activated mast cells?

    <p>They modulate inflammation and immune responses.</p> Signup and view all the answers

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

    <p>Involves antibodies directed against cell surface antigens</p> Signup and view all the answers

    In which type of hypersensitivity are preformed mediators, such as histamine, released from mast cells?

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

    Which of the following substances is not classified as an ingestant?

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

    What indicates an allergic reaction during a skin test?

    <p>Wheal and flare response</p> Signup and view all the answers

    Which of the following is a method of drug therapy for allergies?

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

    What is the result of Ig G or Ig M antibodies reacting with antigens in Type II hypersensitivity?

    <p>Increased antibody-dependent cellular cytotoxicity</p> Signup and view all the answers

    What type of antibody response occurs due to hyposensitization therapy?

    <p>Production of Ig G blocking antibody</p> Signup and view all the answers

    What mechanism is primarily responsible for cell lysis in Type II hypersensitivity reactions?

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

    Which of the following best describes the role of total serum Ig E determination in allergy diagnosis?

    <p>It helps identify potential allergens</p> Signup and view all the answers

    What is the expected outcome of the skin test indicating allergy to a specific allergen?

    <p>Formation of localized erythema</p> Signup and view all the answers

    Which cells are primarily active in antibody-dependent cellular cytotoxicity (ADCC)?

    <p>Eosinophils, macrophages, neutrophils, and CD8 T cells</p> Signup and view all the answers

    Which clinical condition is associated with cytotoxic reactions involving antibodies against muscle acetylcholine receptors?

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

    What triggers hyperacute graft rejection?

    <p>Pre-existing antibodies against the graft</p> Signup and view all the answers

    Which disorders exemplify non-cytotoxic Type II hypersensitivity?

    <p>Graves’ disease and Hashimoto’s thyroiditis</p> Signup and view all the answers

    In Type III hypersensitivity reactions, what is the primary outcome of immune complex deposition?

    <p>Tissue injury and inflammation</p> Signup and view all the answers

    What type of antibodies form immune complexes in Type III hypersensitivity reactions?

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

    Which condition results from drug reactions where antibodies target cell-drug complexes?

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

    What is the main role of the reticuloendothelial system in Type III hypersensitivity?

    <p>To remove immune complexes from circulation</p> Signup and view all the answers

    What is one consequence of platelet aggregation in the formation of antigen-antibody complexes?

    <p>Formation of microthrombi</p> Signup and view all the answers

    Which of the following best describes the function of anaphylatoxins released from complement activation?

    <p>Enhancing vascular permeability</p> Signup and view all the answers

    What type of immune response is characterized by persistent inflammation due to immune complexes?

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

    Which clinical condition is an example of a Type III hypersensitivity reaction?

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

    What is a primary factor contributing to the formation of immune complexes in Type III hypersensitivity?

    <p>Repeated exposure to antigens</p> Signup and view all the answers

    Which immune cells are primarily attracted to the site of immune complex deposition in Type III hypersensitivity?

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

    What is one of the consequences of histamine release during the immune complex response?

    <p>Increasing vascular permeability</p> Signup and view all the answers

    Which of the following is a classic prototype of a Type III hypersensitivity reaction?

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

    What is a systemic immune complex phenomenon that occurs after injection of large doses of foreign serum?

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

    Which of the following symptoms is NOT typically associated with serum sickness?

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

    Which clinical condition is characterized by immune complex deposition in the lungs due to inhalation of dust or mold spores?

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

    In Type IV hypersensitivity reactions, what cells are primarily involved in the cell-mediated immunity process?

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

    Which statement accurately describes the sequence of events in a Type IV hypersensitivity reaction?

    <p>TH cells become activated by IL-1 from macrophages.</p> Signup and view all the answers

    Which of the following is NOT an example of a condition associated with Type III hypersensitivity?

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

    Immune complexes are deposited in small blood vessels leading to which of the following conditions?

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

    What type of hypersensitivity reaction is primarily mediated by antibodies?

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

    Study Notes

    Hypersensitivity Reactions

    • Defined as exaggerated immune responses that are harmful to the host.

    Types of Hypersensitivity

    • There are four types, categorized based on the primary mechanisms: Type I, Type II, Type III, and Type IV.
    • Types I, II, and III involve antibody-mediated immune mechanisms.
    • Type IV is cell-mediated, involving T cell activation and cytokine production.

    Type I: Immediate Hypersensitivity

    • Also known as anaphylaxis, this reaction is triggered by IgE antibodies.
    • IgE binds to mast cells and basophils, leading to the release of various mediators upon antigen exposure.
    • Mediators include histamine, leukotrienes, prostaglandins, and platelet-activating factor.
    • Manifestations range from localized allergic responses (e.g., hay fever, food allergies) to systemic anaphylaxis (life-threatening).
    • Diagnosis involves careful history-taking, skin tests to identify allergens, and measuring IgE levels.
    • Management includes allergen avoidance, hyposensitization, and drug therapy (e.g., corticosteroids, epinephrine, antihistamines).

    Type II: Cytotoxic or Cytolytic Reactions

    • Mediated by IgG or IgM antibodies that target antigens on cell surfaces.
    • These antibodies can trigger cell lysis through complement activation, enhance phagocytosis via opsonization, or promote antibody-dependent cellular cytotoxicity (ADCC).
    • Clinical examples include ABO incompatibility reactions, Rh incompatibility leading to hemolytic disease of the newborn, autoimmune diseases (e.g., autoimmune hemolytic anemia, myasthenia gravis), and graft rejection.

    Type III: Immune Complex Mediated Reaction

    • Occurs when IgG or IgM antibodies complex with soluble antigens.
    • Immune complexes can be deposited in tissues, primarily in the basement membranes of blood vessels, triggering inflammation.
    • Clinical examples include Arthus reaction, serum sickness, post-streptococcal glomerulonephritis, hypersensitivity pneumonitis (e.g., farmer's lung), and some autoimmune diseases like systemic lupus erythematosus (SLE) and rheumatoid arthritis.

    Type IV: Cell Mediated (Delayed Type) Hypersensitivity

    • Distinguished from the immediate types (I-III) as it doesn't involve antibody directly.
    • It is a cell-mediated response driven by T cells and cytokines.
    • This type of hypersensitivity is characterized by a delayed reaction (hours to days) after antigen exposure.
    • Examples include contact dermatitis (e.g., poison ivy), tuberculin reaction, graft rejection, and autoimmune diseases involving T cell-mediated tissue damage.

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    Hypersensitivity Reactions PDF

    Description

    This quiz provides an overview of hypersensitivity reactions, including their definition and the four types categorized by immune response mechanisms. It delves into Type I hypersensitivity, discussing its triggers, mediators, and management strategies. Test your understanding of these crucial immunological concepts.

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