Immune Pathology I: Hypersensitivity Reactions
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Questions and Answers

In hypersensitivity reactions, which type involves IgE?

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

    • Which type of hypersensitivity reaction is characterized by T cell-mediated damage?

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

    • What type of hypersensitivity reaction is associated with Th2 cytokine release?

  • Type I
  • Type IVa
  • Type II
  • Type IVb (correct)

    • Which of the following is an example of a Type IVc hypersensitivity reaction?

    <p>SJS/TEN</p> Signup and view all the answers

    What is a characteristic of Type IVd hypersensitivity reactions?

    <p>Th17-mediated neutrophilic inflammation</p> Signup and view all the answers

    In a Type III hypersensitivity reaction, which type of antibodies are involved?

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

    What is the primary mechanism of Type I hypersensitivity reactions?

    <p>Mast-cell mediated – acute recruitment of basophils, eosinophils</p> Signup and view all the answers

    Which disease is likely to be a combination of type IVa and type IIa hypersensitivity reactions?

    <p>Type 1 diabetes</p> Signup and view all the answers

    What is the primary mechanism of Type IIa hypersensitivity reactions?

    <p>Antibody-mediated cytotoxic reactions</p> Signup and view all the answers

    Which of the following diseases is likely to involve type IVc hypersensitivity reactions?

    <p>Multiple Sclerosis</p> Signup and view all the answers

    What is the primary mechanism of Type IIb hypersensitivity reactions?

    <p>Antibody-mediated ligand-receptor interactions</p> Signup and view all the answers

    What is a common feature of many hypersensitivity reactions?

    <p>Involvement of multiple types of hypersensitivity</p> Signup and view all the answers

    What is the main characteristic of hypersensitivity reactions?

    <p>An excessive and/or pathogenic immune response to either foreign or self antigens</p> Signup and view all the answers

    What is the other name for Type I hypersensitivity?

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

    How many types of hypersensitivity reactions were classified in 1963?

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

    What type of hypersensitivity reaction is characterized by T-cell mediated reactions?

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

    What is the primary mediator of Type I hypersensitivity reactions?

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

    What type of hypersensitivity reaction is characterized by immune-complex reactions?

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

    Which type of hypersensitivity reaction involves the activation of mast cells with IgE and Th2 cytokines?

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

    What is the result of the binding of antibodies to a cell component or a matrix component in Type II hypersensitivity?

    <p>All of the above</p> Signup and view all the answers

    What is the characteristic time course of symptoms for Type I hypersensitivity reactions?

    <p>Rapid - minutes to &lt; 2 days</p> Signup and view all the answers

    What is the primary mechanism of tissue damage in Type III hypersensitivity?

    <p>Formation of antigen-antibody complexes</p> Signup and view all the answers

    Which type of hypersensitivity reaction is characterized by the activation of T cells and the recruitment of eosinophils and basophils?

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

    What is the typical outcome of the late-phase response in Type I hypersensitivity?

    <p>Airway obstruction</p> Signup and view all the answers

    Which type of hypersensitivity reaction involves the binding of antibodies to self-antigens?

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

    What is the primary role of eosinophils in the late-phase response of Type I hypersensitivity?

    <p>Releasing proteolytic enzymes</p> Signup and view all the answers

    Which type of hypersensitivity reaction is characterized by the formation of immune complexes?

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

    What is the typical time course of the late-phase response in Type I hypersensitivity?

    <p>2-12 hours</p> Signup and view all the answers

    What is the typical outcome of the deposition of immune complexes in areas of high pressure or filtration?

    <p>Fibrinoid necrosis of blood vessels</p> Signup and view all the answers

    What is the role of Th cells in Type IV Hypersensitivity Reactions?

    <p>They play a major role in the pathogenesis</p> Signup and view all the answers

    What is the typical time frame for the development of Type IV Hypersensitivity Reactions?

    <p>Months to years</p> Signup and view all the answers

    What is the characteristic histopathological feature of Type III Hypersensitivity Reactions?

    <p>Fibrinoid necrosis of assorted blood vessels</p> Signup and view all the answers

    What is the role of complement in Type III Hypersensitivity Reactions?

    <p>It plays a large role in the tissue damage</p> Signup and view all the answers

    What is the characteristic feature of the immune complexes that form in Type III Hypersensitivity Reactions?

    <p>They are insoluble and stimulate robust inflammation</p> Signup and view all the answers

    What type of hypersensitivity reaction is characterized by granuloma formation and a Th1 response?

    <p>Type IVa Hypersensitivity Reaction</p> Signup and view all the answers

    What is the typical outcome of vasculitis in Type III Hypersensitivity Reactions?

    <p>The vessel is occluded</p> Signup and view all the answers

    What is a common characteristic of chronic inflammation?

    <p>It lasts weeks, months, or years</p> Signup and view all the answers

    What is a risk factor for a wide range of diseases?

    <p>Visceral obesity</p> Signup and view all the answers

    What is a characteristic of granulomatous inflammation?

    <p>It is a type of chronic inflammation</p> Signup and view all the answers

    What is a difference between chronic and acute inflammation?

    <p>Chronic inflammation lasts longer</p> Signup and view all the answers

    What is a common underlying cause of chronic inflammation?

    <p>All of the above</p> Signup and view all the answers

    What is a consequence of visceral obesity?

    <p>Increased risk of diabetes</p> Signup and view all the answers

    What is a characteristic of wound healing?

    <p>It involves both inflammation and tissue repair</p> Signup and view all the answers

    What is a type of disease that can have a chronic inflammatory component?

    <p>All of the above</p> Signup and view all the answers

    What is the main purpose of granuloma formation?

    <p>To wall off an inflammatory stimulus</p> Signup and view all the answers

    What type of immune response is elicited in immune granulomas?

    <p>Cell-mediated immune response</p> Signup and view all the answers

    What is characteristic of the macrophages in a granuloma?

    <p>They resemble epithelial cells</p> Signup and view all the answers

    What is a giant cell in the context of a granuloma?

    <p>A fusion of multiple macrophages</p> Signup and view all the answers

    What is a characteristic of chronic inflammation in the context of granulomas?

    <p>Chronic inflammation with formation of granulomas</p> Signup and view all the answers

    What is a common cause of granuloma formation?

    <p>Both infectious and autoimmune causes</p> Signup and view all the answers

    What is the role of T-cells in immune granulomas?

    <p>They recognize and respond to antigens</p> Signup and view all the answers

    What is the result of the activation of macrophages in immune granulomas?

    <p>Further antigen presentation and inflammation</p> Signup and view all the answers

    What is a potential consequence of excessive lipid build-up in adipocytes?

    <p>Increased production of IL-6 and TNF-alpha</p> Signup and view all the answers

    Which type of cells predominate in chronic inflammatory responses?

    <p>Macrophages and lymphocytes</p> Signup and view all the answers

    What is a consequence of chronic inflammation in the lungs?

    <p>Impaired gas exchange and restricted lung movement</p> Signup and view all the answers

    What is an example of an endogenous toxin that can cause chronic inflammation?

    <p>Oxidized lipids</p> Signup and view all the answers

    What is a characteristic of autoimmune diseases?

    <p>They result from an inappropriate immune response over a long period of time</p> Signup and view all the answers

    What is a consequence of chronic inflammation in tissues?

    <p>Replacement of damaged cells with fibrotic tissue</p> Signup and view all the answers

    What is a characteristic of allergic diseases?

    <p>They result from an excessive immune response to exogenous allergens</p> Signup and view all the answers

    What is a potential consequence of chronic inflammation in adipocytes?

    <p>Insulin resistance and type II diabetes</p> Signup and view all the answers

    What is the primary function of platelets during the hemostasis phase of healing?

    <p>To form a blood clot and stop bleeding</p> Signup and view all the answers

    What type of cells are particularly implicated in chronic inflammation?

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

    What is the term for the redundant, inflamed synovium that forms in joints during chronic inflammation?

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

    What is the term for the process of blood extravasation into a tissue, followed by platelet activation and blood coagulation?

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

    What type of cells can form lymphatic nodule-appearing regions in areas of chronic inflammation?

    <p>Plasma cells, macrophages, and lymphocytes</p> Signup and view all the answers

    What is the primary difference between healing and scarring?

    <p>Healing results in the restoration of normal tissue function, while scarring results in the formation of non-functional tissue</p> Signup and view all the answers

    What is the typical outcome of frustrated phagocytosis?

    <p>Production of free radicals and proteases</p> Signup and view all the answers

    What is a characteristic feature of caseating granulomas?

    <p>Necrotic core of caseous cellular debris</p> Signup and view all the answers

    What is the primary site of granuloma formation in tuberculosis?

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

    What is the typical outcome of chronic inflammation?

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

    What is the typical spread of tuberculosis in the body?

    <p>Virtually any organ in the body</p> Signup and view all the answers

    What is the term for the necrotic core of cellular debris in caseating granulomas?

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

    Which of the following can lead to the production of IL-6 and TNF-alpha by the adipocyte?

    <p>Excessive lipid build-up</p> Signup and view all the answers

    What type of cells predominate in chronic inflammation?

    <p>Macrophages and lymphocytes</p> Signup and view all the answers

    What is a consequence of chronic inflammation in the respiratory system?

    <p>Thickening of the respiratory membrane and development of granulomas</p> Signup and view all the answers

    What is a common underlying cause of chronic inflammation?

    <p>Prolonged exposure to toxins</p> Signup and view all the answers

    What is a characteristic of chronic inflammation?

    <p>Persistent inflammation with tissue damage and repair</p> Signup and view all the answers

    What is a consequence of visceral obesity?

    <p>Increased risk of chronic inflammation</p> Signup and view all the answers

    What is a characteristic of granulomatous inflammation?

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

    What is the main purpose of granuloma formation?

    <p>To contain and isolate foreign substances or microorganisms</p> Signup and view all the answers

    What is the primary function of classically-activated macrophages?

    <p>To recruit other leukocytes and damage pathogens</p> Signup and view all the answers

    What is the role of alternatively-activated macrophages in tissue repair?

    <p>To promote angiogenesis and fibrosis</p> Signup and view all the answers

    What is the role of macrophages in chronic inflammation?

    <p>To recruit other leukocytes and damage pathogens</p> Signup and view all the answers

    What is the primary function of Langerhans cells?

    <p>To present antigens to T-cells</p> Signup and view all the answers

    What is the role of free radicals in macrophage function?

    <p>To destroy bacteria and remove cellular debris</p> Signup and view all the answers

    What is the role of cytokines in macrophage function?

    <p>To recruit other leukocytes and damage pathogens</p> Signup and view all the answers

    What is the role of macrophages in the resolution of inflammation?

    <p>To suppress inflammation and resolve tissue damage</p> Signup and view all the answers

    What is the primary function of dendritic cells?

    <p>To present antigens to T-cells</p> Signup and view all the answers

    What is the primary function of platelets during the hemostasis phase of wound healing?

    <p>To form a blood clot and stop bleeding</p> Signup and view all the answers

    Which type of cells are particularly implicated in chronic inflammation and are recruited to sites of chronic inflammation by macrophages?

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

    What is the term for the redundant, inflamed synovium that forms in joints during chronic inflammation?

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

    During the process of wound healing, what is the term for the formation of new blood vessels through the proliferation of endothelial cells?

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

    What is the term for the structure that forms when plasma cells, macrophages, and lymphocytes aggregate in an area of chronic inflammation?

    <p>Tertiary lymphoid organ</p> Signup and view all the answers

    During the process of wound healing, what is the primary function of vasodilation?

    <p>To allow for the delivery of oxygen and nutrients to the wound site</p> Signup and view all the answers

    What is the main characteristic of the necrotic core in a caseating granuloma?

    <p>It is composed of a cheesy, amorphous material with no distinct cellular structures.</p> Signup and view all the answers

    What is the result of frustrated phagocytosis in foreign-body granulomas?

    <p>Production of free radicals and proteases that can damage extracellular matrix and viable cells.</p> Signup and view all the answers

    What is the primary location of granulomas in tuberculosis?

    <p>Lung tissue</p> Signup and view all the answers

    What type of granuloma is characterized by a necrotic core surrounded by epitheloid macrophages and lymphocytes?

    <p>Caseating granuloma</p> Signup and view all the answers

    What is the role of macrophages in granuloma formation?

    <p>To surround and isolate the foreign body or antigen.</p> Signup and view all the answers

    What is the characteristic feature of chronic inflammation in the context of granulomas?

    <p>The formation of granulomas around a foreign body or antigen.</p> Signup and view all the answers

    What is the primary function of giant cells in a granuloma?

    <p>To perform the 'walling-off' function of a granuloma</p> Signup and view all the answers

    What is the characteristic of the adaptive immune system involved in immune granulomas?

    <p>It involves a cell-mediated immune response</p> Signup and view all the answers

    What is the net result of chronic inflammation in the context of granulomas?

    <p>Replacement of normal tissue by fibrosis</p> Signup and view all the answers

    What is the role of IFN-gamma in immune granulomas?

    <p>It contributes to the activation of macrophages</p> Signup and view all the answers

    What is the characteristic of macrophages in a granuloma?

    <p>They resemble epithelial cells</p> Signup and view all the answers

    What is the type of hypersensitivity reaction characterized by granuloma formation and a Th1 response?

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

    What is the role of T-cells in immune granulomas?

    <p>They produce IL-2 and IFN-gamma</p> Signup and view all the answers

    What is the characteristic of the inflammatory stimulus in immune granulomas?

    <p>It is difficult to eradicate or it elicits a Th1 +/- Th17 response</p> Signup and view all the answers

    Study Notes

    Hypersensitivity Reactions - Overview

    • Hypersensitivity reactions are excessive and/or pathogenic immune responses to foreign or self-antigens.
    • Classified into four types: I, II, III, and IV.

    Hypersensitivity Reactions - Classification

    • Type I (IgE-mediated hypersensitivity):
      • Immediate hypersensitivity reaction
      • Involves mast cells, basophils, and eosinophils
      • Examples: anaphylaxis, angioedema, urticaria (hives), asthma, allergic rhinitis
    • Type II (antibody-mediated cytotoxic reactions):
      • Antibodies bind to cell surface or matrix components
      • Examples: immune destruction of RBCs or platelets, rheumatic fever
    • Type III (immune-complex reactions):
      • Immune complexes deposit in tissues, leading to inflammation
      • Examples: lupus, vasculitis, renal glomerular disorders
    • Type IV (delayed-type hypersensitivity):
      • T-cell-mediated reactions
      • Examples: granulomatous disease, T1DM, MS
      • Subtypes: IVa, IVb, IVc, and IVd

    Type I Hypersensitivity - Pathogenesis

    • Two phases: immediate and late-phase responses
    • Immediate response: mast cell degranulation, edema, and smooth muscle contraction
    • Late-phase response: recruitment of basophils and eosinophils, leading to tissue damage

    Type II Hypersensitivity

    • Antibodies bind to cell surface or matrix components
    • Activation of complement, antibody-dependent cell-mediated cytotoxicity, and inflammation
    • Examples: Graves' disease, myasthenia gravis

    Type III Hypersensitivity

    • Immune complexes deposit in tissues, leading to inflammation and tissue damage
    • Examples: vasculitis, lupus, renal glomerular disorders

    Type IV Hypersensitivity

    • Extremely variable, depending on the disease
    • Examples: granuloma formation (IVa), eosinophilic inflammation (IVb), cytotoxic T-cell activation (IVc), and Th17-mediated inflammation (IVd)

    Organizing Hypersensitivity Reactions

    • Are antibodies involved? (IgE, IgG, IgM)
    • Are T-cells thought to be the major pathologic players?
    • Is there a particular Th subtype involved? (Th1, Th2, Th17)
    • Time course of symptoms: rapid (minutes to <2 days), subacute (days to weeks), or chronic (months to years)

    Chronic Inflammation

    • Chronic inflammation lasts for weeks, months, or years, characterized by the coexistence of inflammation, tissue injury, and tissue repair.
    • Chronic inflammation can result from the inability to resolve acute inflammation, autoimmune disease, or continuous damage to an organ or tissue.

    Chronic Inflammation and Obesity

    • Visceral obesity is a risk factor for various diseases, including diabetes, atherosclerosis, metabolic syndrome, and cancer.
    • Excessive lipid buildup in adipocytes can stress them, leading to the production of reactive oxygen species (ROS).
    • Free fatty acids at high concentrations can bind to pattern recognition receptors (PAMP-R) within adipocytes, leading to the production of pro-inflammatory cytokines IL-6 and TNF-alpha, which contribute to insulin resistance and eventually type II diabetes.

    Causes of Chronic Inflammation

    • Persistent infections can lead to chronic inflammation, characterized by the predominance of macrophages and lymphocytes, replacement of parenchymal cells with fibrotic tissue, and impaired tissue function.
    • Immune-mediated inflammatory diseases, such as autoimmune and allergic diseases, can also cause chronic inflammation.
    • Prolonged exposure to toxins, either exogenous (e.g., silica) or endogenous (e.g., VEGF, NO), can also contribute to chronic inflammation.

    Chronic Inflammation and Lymphocytes

    • Cytotoxic T-cells are particularly implicated in chronic inflammation, recruited to sites of inflammation by macrophages that continue to respond to the inflammatory stimulus.
    • Plasma cells may be recruited to inflamed areas, forming lymphatic nodule-appearing regions known as tertiary lymphoid organs, prominent in some autoimmune diseases (e.g., rheumatoid arthritis).

    Healing and Scarring

    • The healing process involves phases, including hemostasis, inflammation, proliferation, and remodeling.
    • Chronic inflammation can lead to the replacement of normal tissue with fibrosis, resulting in scarring.

    Granuloma Formation

    • Granulomas are an attempt by lymphocytes and macrophages to "wall off" an inflammatory stimulus, characterized by a microscopic aggregation of macrophages transformed into epithelium-like cells, surrounded by lymphocytes and occasionally plasma cells.
    • Granuloma-causing conditions include tuberculosis, leprosy, syphilis, sarcoidosis, and Crohn's disease.
    • Immune granulomas involve the adaptive immune system, with a cell-mediated immune response (Type IV hypersensitivity) elicited in response to an inflammatory stimulus.

    Tuberculosis

    • Tuberculosis was once the leading cause of death, characterized by the formation of large, widely-disseminated granulomas that destroy lung tissue and lead to pleural effusions.
    • The pathological hallmark of tuberculosis is the caseating granuloma, characterized by epitheloid macrophages and lymphocytes surrounding a necrotic core of caseous cellular debris.

    Chronic Inflammation

    • Excessive lipid buildup can stress adipocytes, leading to the production of IL-6 and TNF-alpha, which can cause insulin resistance and eventually type II diabetes.
    • Chronic inflammation can lead to the replacement of parenchyma with fibrotic tissue, which can impair gas exchange and restrict lung movement.

    Causes of Chronic Inflammation

    • Persistent infections can lead to chronic inflammation, characterized by the predominance of macrophages and lymphocytes.
    • Immune-mediated inflammatory diseases, such as autoimmune and allergic diseases, can cause chronic inflammation.
    • Prolonged exposure to toxins, both exogenous and endogenous, can lead to chronic inflammation.

    The Role of Macrophages in Chronic Inflammation

    • Macrophages play a crucial role in chronic inflammation, with two main functions:
      • Pro-inflammatory macrophage functions: destroying bacteria, producing free radicals, secreting cytokines and growth factors, and recruiting other leukocytes.
      • Macrophage functions of particular interest in chronic inflammation: destroying bacteria, secreting cytokines and growth factors, and contributing to fibrosis and angiogenesis.

    Macrophage Responses in Chronic Inflammation

    • Macrophage responses can evolve as inflammation and damage continue in a tissue.
    • Two main types of macrophage activation:
      • Classically-activated macrophages: recruit other leukocytes, damage pathogens, and often damage bystander host cells.
      • Alternatively-activated macrophages: promote angiogenesis, fibrosis, and tissue repair.

    Repair and Macrophages

    • Angiogenesis is a critical step in tissue repair, involving vasodilation, pericyte separation, endothelial migration, and proliferation of endothelial cells.
    • Fibrosis and chronic inflammation are closely linked, with macrophages playing a key role in promoting fibrosis.

    Chronic Inflammation and Lymphocytes

    • Cytotoxic T-cells are particularly implicated in chronic inflammation, recruited to sites of inflammation by macrophages that continue to respond to the inflammatory stimulus.
    • Plasma cells may be recruited to inflamed areas, forming lymphatic nodule-appearing regions in an area of chronic inflammation.

    Granulomas and Chronic Inflammation

    • A granuloma is an attempt by lymphocytes and macrophages to "wall off" an inflammatory stimulus.
    • Granuloma-causing conditions include tuberculosis, leprosy, syphilis, sarcoidosis, and Crohn's disease.
    • Immune granulomas involve the adaptive immune system, with a cell-mediated immune response elicited.

    Chronic Inflammation and Healing

    • The steps of healing include hemostasis, inflammation, proliferation, and remodeling.
    • Chronic inflammation can lead to scarring, with the formation of fibrotic tissue replacing normal tissue.
    • Granulomas can form in response to chronic inflammation, with macrophages and lymphocytes aggregating to "wall off" the inflammatory stimulus.

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