Hypersensitivity Reactions Quiz
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Questions and Answers

What is the primary characteristic of Type I hypersensitivity reactions?

  • It occurs several hours after exposure to an allergen.
  • It causes immune complex formation.
  • It involves mast cells and IgE antibodies. (correct)
  • It is mediated by IgG antibodies.

    • Which of the following best describes an exogenous antigen?

  • Antigens produced by the body due to autoimmune reactions.
  • Antigens derived from environmental sources such as dust or pollen. (correct)
  • Antigens that are primarily genetic in origin.
  • Protein fragments created as a immune response in the host.

    • What role do HLA genes play in hypersensitivity disorders?

  • They are responsible for storing histamine in mast cells.
  • They enhance the immune response to all allergens equally.
  • They contribute to genetic susceptibility to hypersensitivity diseases. (correct)
  • They help in the elimination of self-antigens.

    • Which of the following statements is TRUE regarding Type II hypersensitivity reactions?

    <p>They are antibody-mediated disorders focused on cellular targets.</p> Signup and view all the answers

    In which percentage of the population do Type I hypersensitivity reactions typically occur?

    <p>10-20%</p> Signup and view all the answers

    What triggers the immediate reaction seen in Type I hypersensitivity?

    <p>Interaction between an allergen and IgE antibodies.</p> Signup and view all the answers

    Which type of hypersensitivity involves immune complex-mediated disorders?

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

    Which of the following is NOT a feature of hypersensitivity disorders?

    <p>All hypersensitivity reactions occur immediately.</p> Signup and view all the answers

    What is necessary for an individual to be classified as genetically susceptible to type I hypersensitivity reactions?

    <p>Presence of atopy due to genetic factors</p> Signup and view all the answers

    Which cytokine primarily stimulates B cells to produce IgE antibodies during the sensitization process?

    <p>IL-4</p> Signup and view all the answers

    What is the primary role of mast cells in type I hypersensitivity reactions?

    <p>To release mediators that cause allergic symptoms</p> Signup and view all the answers

    What triggers the degranulation of mast cells during re-exposure to an allergen?

    <p>The cross-linking of IgE antibodies on their surface</p> Signup and view all the answers

    During which phase of an allergic reaction do symptoms typically begin to manifest after allergen exposure?

    <p>Immediate phase response</p> Signup and view all the answers

    What is a characteristic feature of the immediate phase response in type I hypersensitivity?

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

    In the context of allergic reactions, what is the function of eosinophils activated by IL-5?

    <p>To mediate inflammatory responses and tissue damage</p> Signup and view all the answers

    What type of cells are primarily linked to the initiation of type I hypersensitivity reactions through antigen presentation?

    <p>Antigen presenting cells (APCs)</p> Signup and view all the answers

    What is a characteristic feature of the early-phase reaction in type I hypersensitivity?

    <p>Release of preformed mediators</p> Signup and view all the answers

    Which of the following best describes the late-phase reaction in type I hypersensitivity?

    <p>It is characterized by the infiltration of eosinophils and neutrophils.</p> Signup and view all the answers

    What type of hypersensitivity includes conditions such as hay fever and extrinsic asthma?

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

    What might a systemic type I hypersensitivity reaction lead to if severe?

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

    In type II hypersensitivity reactions, which antibodies are most commonly involved?

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

    Which mechanism is NOT a potential effect of the antigen-antibody reaction in type II hypersensitivity?

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

    What type of inflammatory infiltrate is primarily observed in allergic nasal polyps associated with type I hypersensitivity?

    <p>Eosinophils and inflammatory cells</p> Signup and view all the answers

    Which of the following correctly describes the role of secondary mediators in the late-phase reaction of type I hypersensitivity?

    <p>They consist of cytokines and leukotrienes that contribute to prolonged inflammation.</p> Signup and view all the answers

    What is the primary mechanism by which antibodies lead to the lysis of target cells in Type II hypersensitivity reactions?

    <p>Activating the complement system</p> Signup and view all the answers

    In the context of antibody-dependent cellular cytotoxicity (ADCC), which component directly links natural killer cells to target cells?

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

    Which of the following conditions is associated with antibodies that act as agonists on their target receptors?

    <p>Grave's disease</p> Signup and view all the answers

    What type of blood cells are primarily involved in hemolytic disease of the newborn (erythroblastosis foetalis)?

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

    Which type of immune response is characterized by the opsonization of cells and their subsequent phagocytosis by macrophages?

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

    Which of the following is NOT a characteristic of Type II hypersensitivity reactions?

    <p>Immediate hypersensitivity reaction</p> Signup and view all the answers

    What is the consequence of penicillin binding to red blood cells in the context of Type II hypersensitivity?

    <p>IgG antibodies being formed against the modified RBCs</p> Signup and view all the answers

    What type of antibodies cause ineffective cell function without direct injury or inflammation in conditions such as Hashimoto's thyroiditis?

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

    Study Notes

    Hypersensitivity Reactions

    • Hypersensitivity reaction is an exaggerated immune response to an antigen leading to tissue damage, disease, or even death in a previously sensitized individual
    • Hypersensitivity reactions are classified into four main types: Type I, Type II, Type III, and Type IV

    Type I (Immediate) Hypersensitivity Reactions

    • Also known as allergic or atopic reactions
    • Occurs within minutes (5-10 minutes) after antigen (allergen) interacts with IgE antibodies bound to mast cells
    • Mediated by IgE antibodies
    • Develops in genetically susceptible individuals who are atopic
    • Common examples include bronchial asthma, hay fever, and food allergies

    Mechanism of Type I Hypersensitivity Reactions

    • Initial Exposure (Sensitization)

      • Antigen (allergen) enters the body through inhalation, ingestion, or injection
      • Antigen is presented to T cells by antigen-presenting cells (APCs) like macrophages
      • T cells differentiate into TH2 cells
      • TH2 cells release cytokines (IL-4, IL-5, and IL-13)
      • IL-4 stimulates B cells to produce IgE antibodies
      • IL-5 activates eosinophils
      • IL-13 stimulates epithelial cells to produce mucus
      • IgE antibodies bind to Fc receptors on mast cells and basophils

    • Re-exposure to Antigen (Degranulation)

      • Re-exposure cross-links IgE molecules on mast cells and basophils
      • This triggers degranulation, releasing mediators like histamine, cytokines, prostaglandins, and leukotrienes
      • Mediators cause immediate reactions: vasodilation, increased vascular permeability, smooth muscle contraction, increased glandular secretions
      • Late-phase reaction (2-8 hours) involves release of secondary mediators, tissue infiltration by inflammatory cells, and mucosal damage

    Localized Type I Hypersensitivity Reactions

    • Examples: Hay fever and extrinsic asthma
    • Hay fever: Acute inflammation of the nasal and conjunctival mucosa with sneezing and hypersecretion after allergen exposure
    • Bronchial asthma: Wheezing and respiratory distress caused by bronchospasm and increased mucus secretion after allergen exposure

    Systemic Type I Hypersensitivity Reactions

    • Anaphylactic reactions: Severe, life-threatening allergic response characterized by shock, hypotension, widespread urticaria, and dyspnea
    • Often triggered by drug injections, food allergies, or insect stings

    Type II (Antibody-Mediated) Hypersensitivity Reactions

    • Antibodies directed against specific antigens on cell surfaces cause cell lysis or dysfunction
    • Mediated by IgG (usually) and IgM (rarely) antibodies
    • Antigens can be endogenous (self) or exogenous (adsorbed on cell surfaces or extracellular matrix)
    • Mechanisms:
      • Complement-dependent cytotoxicity
      • Antibody-dependent cellular cytotoxicity (ADCC)
      • Antibody-mediated cellular dysfunction (e.g. Graves' disease, Hashimoto's thyroiditis)

    Complement-Dependent Cytotoxicity (Type II Hypersensitivity)

    • Antibodies activate complement system, leading to cell lysis
    • Examples:
      • Transfusion reactions (ABO or Rh incompatibility)
      • Autoimmune hemolytic anemia

    Antibody-Dependent Cellular Cytotoxicity (ADCC) (Type II Hypersensitivity)

    • Antibodies bind to target cells, facilitating their destruction by NK cells or macrophages
    • Does not involve complement activation or phagocytosis
    • Target cell killing occurs through the release of perforin and granzyme by NK cells

    Antibody-Mediated Cellular Dysfunction (Type II Hypersensitivity)

    • Antibodies block or interfere with cell surface receptor function
    • Examples:
      • Hashimoto's thyroiditis: Antibodies against TSH receptor block TSH binding, leading to hypothyroidism
      • Graves' disease: Antibodies against TSH receptor act as TSH, leading to hyperthyroidism

    Examples of Type II Hypersensitivity Reactions

    • Blood cells:

      • Autoimmune hemolytic anemia
      • Transfusion reactions
      • Hemolytic disease of the newborn (erythroblastosis fetalis)
      • Idiopathic thrombocytopenic purpura (ITP)
      • Drug-induced cytotoxic antibodies

    • Tissue components:

      • Myasthenia gravis (antibodies against acetylcholine receptor)
      • Goodpasture's syndrome (antibodies against basement membrane of kidneys and lungs)
      • Pemphigus vulgaris (antibodies against desmosomes in skin)

    ### Note: This is not an exhaustive list of all the details included in the document but a summarized structure of key topics and their essential details.

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    Description

    Test your knowledge on hypersensitivity reactions, focusing on the types and mechanisms involved. This quiz covers Type I (Immediate) hypersensitivity reactions, their triggers, and the biological responses elicited. Perfect for students of immunology or medical sciences.

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