Podcast
Questions and Answers
Which type of hypersensitivity reaction is characterized by T-cell-mediated inflammation?
Which type of hypersensitivity reaction is characterized by T-cell-mediated inflammation?
What is a common feature of Type I hypersensitivity reactions?
What is a common feature of Type I hypersensitivity reactions?
Which of the following is NOT a risk factor for Type IV hypersensitivity?
Which of the following is NOT a risk factor for Type IV hypersensitivity?
For which type of hypersensitivity is prior exposure indicated by a positive Mantoux test?
For which type of hypersensitivity is prior exposure indicated by a positive Mantoux test?
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Which statement about Type II hypersensitivity is correct?
Which statement about Type II hypersensitivity is correct?
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What initiates the production of IgE antibodies in Type I hypersensitivity reactions?
What initiates the production of IgE antibodies in Type I hypersensitivity reactions?
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Which clinical manifestation is associated with Type I hypersensitivity reactions?
Which clinical manifestation is associated with Type I hypersensitivity reactions?
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What is the mechanism of action behind Type II hypersensitivity reactions?
What is the mechanism of action behind Type II hypersensitivity reactions?
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Which of the following conditions is an example of Type II hypersensitivity?
Which of the following conditions is an example of Type II hypersensitivity?
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In Type I hypersensitivity, which substance is primarily released by mast cells upon re-exposure to an allergen?
In Type I hypersensitivity, which substance is primarily released by mast cells upon re-exposure to an allergen?
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What are commonly associated risk factors for Type I hypersensitivity reactions?
What are commonly associated risk factors for Type I hypersensitivity reactions?
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Which of the following best describes Type II hypersensitivity reactions?
Which of the following best describes Type II hypersensitivity reactions?
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What is a key characteristic of Type I hypersensitivity reactions regarding their transmissibility?
What is a key characteristic of Type I hypersensitivity reactions regarding their transmissibility?
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What is the primary cause of Type III Hypersensitivity?
What is the primary cause of Type III Hypersensitivity?
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What occurs during the sensitization phase of Type IV Hypersensitivity?
What occurs during the sensitization phase of Type IV Hypersensitivity?
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Which statement accurately describes the pathophysiology of Type III Hypersensitivity?
Which statement accurately describes the pathophysiology of Type III Hypersensitivity?
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What type of agents can trigger Type IV Hypersensitivity?
What type of agents can trigger Type IV Hypersensitivity?
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Which of the following autoimmune diseases is categorized under Type III Hypersensitivity?
Which of the following autoimmune diseases is categorized under Type III Hypersensitivity?
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In Type IV Hypersensitivity, which cells are primarily involved in the delayed inflammatory response?
In Type IV Hypersensitivity, which cells are primarily involved in the delayed inflammatory response?
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What kind of response is characterized by the recruitment of neutrophils in Type III Hypersensitivity?
What kind of response is characterized by the recruitment of neutrophils in Type III Hypersensitivity?
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Study Notes
Hypersensitivity Reactions
- Hypersensitivity reactions are immune responses that cause harm rather than benefit.
- Four main types of hypersensitivity reactions exist: Type I, Type II, Type III, and Type IV.
Type I Hypersensitivity (Immediate/Allergic Reactions)
- Cause: Exposure to allergens like pollen, pet dander, food, insect venom, or medications.
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Pathophysiology:
- Sensitization phase: Initial exposure triggers IgE antibody production, binding to mast cells and basophils.
- Re-exposure: Subsequent exposure causes cross-linking of IgE, triggering mast cell degranulation and release of histamine, leukotrienes, prostaglandins.
- This leads to increased vascular permeability, smooth muscle contraction, and mucus secretion.
- Clinical Manifestations: Urticaria (hives), allergic rhinitis (hay fever), asthma, and anaphylaxis.
- Transmission: Not transmissible; a response triggered by exposure to allergens.
- Risk Factors: Genetic predisposition to atopy (family history of allergies, asthma, or eczema), environmental exposure to allergens, and occupation-related exposure.
Type II Hypersensitivity (Cytotoxic Reactions)
- Cause: Autoimmune disorders (e.g., Graves' disease, Myasthenia gravis) and blood transfusion reactions where the body's immune system targets its own tissues (self-antigens) or foreign antigens.
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Pathophysiology:
- Antibodies (IgG or IgM) bind to antigens on cell surfaces.
- This leads to opsonization and phagocytosis by macrophages.
- Complement system activation causes cell lysis and death.
- Examples: Graves' disease (antibodies bind to TSH receptors), Myasthenia gravis (antibodies block acetylcholine receptors).
- Transmission: Not transmissible; a result of the body's immune response to self or foreign antigens.
Type III Hypersensitivity (Immune Complex-Mediated)
- Cause: Formation of immune complexes (antigen-antibody complexes) that deposit in tissues, leading to inflammation.
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Pathophysiology:
- Circulating immune complexes become trapped in blood vessels or tissues.
- Complement activation recruits neutrophils, releasing enzymes causing tissue damage.
- Inflammation and necrosis result in organ damage.
- Examples: Systemic lupus erythematosus (SLE), rheumatoid arthritis (RA).
- Transmission: Not transmissible; a result of the body's immune response to self or foreign antigens.
- Risk Factors: Autoimmune diseases (e.g., SLE and RA), chronic infections.
Type IV Hypersensitivity (Delayed/Cell-Mediated)
- Cause: Exposure to environmental antigens (e.g., poison ivy), medications, or infectious agents.
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Pathophysiology:
- Sensitization phase: Memory T cells are generated after initial exposure.
- Re-exposure: Activates memory T cells, releasing cytokines like IFN-γ and TNF-α.
- Delayed inflammatory response leads to macrophage recruitment and tissue damage.
- Examples: Contact dermatitis (e.g., poison ivy).
- Transmission: Not transmissible; a result of T-cell-mediated immune responses.
- Risk Factors: Exposure to allergens, topical medications, chemicals like formaldehyde, and infections (e.g., Tuberculosis).
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Description
This quiz covers the immune responses associated with hypersensitivity reactions, specifically focusing on Type I hypersensitivity. Learn about the causes, pathophysiology, clinical manifestations, and risk factors of allergic reactions. Test your knowledge of how the immune system can cause harm through these types of responses.
