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Questions and Answers
What is the role of antibodies in Type III hypersensitivity reactions?
What is the role of antibodies in Type III hypersensitivity reactions?
Which feature distinguishes Type IV hypersensitivity from the other types?
Which feature distinguishes Type IV hypersensitivity from the other types?
What is a clinical example of a systemic immune complex-mediated disease?
What is a clinical example of a systemic immune complex-mediated disease?
What is the primary mechanism that leads to tissue injury in Type III hypersensitivity reactions?
What is the primary mechanism that leads to tissue injury in Type III hypersensitivity reactions?
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What is a characteristic of the Arthus reaction?
What is a characteristic of the Arthus reaction?
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How long does it typically take for Type IV hypersensitivity reactions to occur after antigen exposure?
How long does it typically take for Type IV hypersensitivity reactions to occur after antigen exposure?
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What is primarily involved in the pathogenesis of Type IV hypersensitivity reactions?
What is primarily involved in the pathogenesis of Type IV hypersensitivity reactions?
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Which condition is typically associated with localized immune complex-mediated disease?
Which condition is typically associated with localized immune complex-mediated disease?
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Which aspect is incorrectly associated with Type III hypersensitivity?
Which aspect is incorrectly associated with Type III hypersensitivity?
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Which of the following is NOT a feature of Type IV hypersensitivity?
Which of the following is NOT a feature of Type IV hypersensitivity?
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What is the mechanism by which CD4+ T-helper cells contribute to granuloma formation?
What is the mechanism by which CD4+ T-helper cells contribute to granuloma formation?
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Which type of hypersensitivity reaction is characterized by a delayed response and is mediated by CD4+ T-helper cells?
Which type of hypersensitivity reaction is characterized by a delayed response and is mediated by CD4+ T-helper cells?
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What role do CD8+ T cells play in the immune response?
What role do CD8+ T cells play in the immune response?
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Which cytokines are secreted by activated Th17 cells during an inflammatory reaction?
Which cytokines are secreted by activated Th17 cells during an inflammatory reaction?
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Which condition is an example of a cytotoxic reaction mediated by CD8+ T cells?
Which condition is an example of a cytotoxic reaction mediated by CD8+ T cells?
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What is commonly used to diagnose an immune response to tuberculosis?
What is commonly used to diagnose an immune response to tuberculosis?
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What is the primary purpose of inflammatory cytokines like IFN-γ and IL-3 in granuloma formation?
What is the primary purpose of inflammatory cytokines like IFN-γ and IL-3 in granuloma formation?
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Allergic contact dermatitis is typically triggered by what type of antigen?
Allergic contact dermatitis is typically triggered by what type of antigen?
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What is a key feature of the cytotoxic response in graft-versus-host disease?
What is a key feature of the cytotoxic response in graft-versus-host disease?
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Which of the following is NOT associated with delayed-type hypersensitivity?
Which of the following is NOT associated with delayed-type hypersensitivity?
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Study Notes
Types of Immune Response
- Hypersensitivity reactions are categorized into types III and IV.
- Type III reactions are immune complex-mediated, triggered by antibodies (IgG and IgM) reacting with soluble antigens (exogenous or endogenous).
- Reactions happen 3-8 hours after antigen exposure, potentially localized or systemic.
- Immune complexes form and deposit in postcapillary venules, leading to complement activation and recruitment of leukocytes.
- Inflammatory reactions, necrotizing vasculitis, and tissue damage result.
- Systemic examples include serum sickness (following passive immunization with foreign serum).
- Localized examples include Arthus reactions (local skin tissue necrosis after antigen injection).
Type IV Hypersensitivity
- Also known as cell-mediated or delayed hypersensitivity (delayed reaction).
- T lymphocytes, dendritic cells, macrophages, and cytokines mediate cell destruction of target cells.
- This occurs 24-72 hours after antigen exposure.
CD4+ Cytokine-Mediated Inflammation (Delayed Hypersensitivity)
- Persistent non-degradable intracellular antigens activate CD4+ T-helper cells (Th1 or Th17).
- These cells release inflammatory mediators (e.g., IFN-γ).
- Macrophages transform into epithelioid cells; granuloma formation results (e.g., Tuberculosis, fungal infections).
Examples of Type IV Hypersensitivity Reactions
- Tuberculin reaction (Mantoux test): A delayed-type hypersensitivity skin test for prior exposure to tuberculosis.
- Granuloma formation: Response to intracellular pathogens (e.g., mycobacteria).
- Reaction against fungal infection: Activated Th17 cells respond, secreting cytokines like IL-17 and IL-22.
- Allergic Contact Dermatitis: Reaction to environmental antigens (e.g., poison ivy).
CD8+ Cell-Mediated Cytotoxic Reaction
- Cytotoxic T lymphocytes (CD8+ T cells) kill target cells by inducing apoptosis (programmed cell death).
- Examples include:
- Killing virus-infected cells
- Killing malignant cells (cancerous cells)
- Type 1 diabetes (islet cell destruction)
- Graft-versus-host disease
- Chronic transplant rejection
- Drug reactions, tattoo/black henna/nickel reactions, etc.
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Description
This quiz explores the various types of immune responses, specifically focusing on hypersensitivity reactions types III and IV. Understand how these reactions are mediated, their time frames, and the potential examples of localized and systemic responses. Test your knowledge on the mechanisms and implications of these immune functions.
