Type III and IV Hypersensitivity Reactions: PBC 9700 Session 12
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Questions and Answers

What is the primary cause of type III hypersensitivity reactions?

  • Antigen-mediated activation of mast cells
  • Deficiency in factor I, C1, or C3
  • Direct interaction between B cells and T cells
  • Formation of immune complexes in the blood or tissues (correct)

    • Which statement accurately describes the pathophysiology of type III reactions?

  • Type III reactions are characterized by direct cytotoxic effects of T cells on self-antigens.
  • Immune complexes form and deposit in tissues, triggering chemotaxis of neutrophils and macrophages. (correct)
  • Complement activation leads to direct destruction of antigens.
  • The primary effector cells involved are natural killer (NK) cells.

    • What role do complement factors C3a and C5a play in type III hypersensitivity reactions?

  • Activate B cells to produce antibodies against immune complexes
  • Inhibit the production of pro-inflammatory cytokines
  • Induce apoptosis of antigen-presenting cells
  • Promote chemotaxis of immune cells to the site of immune complex deposition (correct)

    • Which factor deficiency can reduce clearance of immune complexes and increase susceptibility to type III reactions?

    <p>Factor I deficiency</p> Signup and view all the answers

    In type III hypersensitivity, where do immune complexes deposit if they are not cleared from circulation?

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

    What is the main consequence of complement activation in type III hypersensitivity reactions?

    <p>'Frustrated phagocytosis' and inflammation leading to tissue damage</p> Signup and view all the answers

    What is the predominant T cell response in granulomatous hypersensitivity?

    <p>CD4+ Th1 cell response</p> Signup and view all the answers

    Which cells are recruited to the site of chronic infection in granulomatous hypersensitivity?

    <p>Th1 cells</p> Signup and view all the answers

    What triggers airway macrophages to penetrate into the underlying tissue in granulomatous hypersensitivity?

    <p>TLR engagement</p> Signup and view all the answers

    Which cytokines are released by macrophages in granulomatous hypersensitivity to promote vasodilation and endothelial adhesion molecule expression?

    <p>IL-1β, IL-6, and TNF-α</p> Signup and view all the answers

    What is a characteristic of immune complex deposition in Type III hypersensitivity reactions?

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

    How do T regulatory (Treg) cells aid in the resolution of the inflammatory response?

    <p>By suppressing the inflammatory response</p> Signup and view all the answers

    What triggers the activation of phagocytes by binding to Fc receptors and complement receptors?

    <p>IC and C3b</p> Signup and view all the answers

    Which factor may induce peptidyl arginine deiminases (PAD) activity to generate self-antigens for Rheumatoid Arthritis?

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

    In Rheumatoid Arthritis, what is the role of Rheumatoid Factor (RF)?

    <p>Serves as an indicator of inflammatory and autoimmune activity</p> Signup and view all the answers

    What is the significance of HLA-DR4 in Rheumatoid Arthritis?

    <p>Good at presenting citrullinated self-Antigens</p> Signup and view all the answers

    Which disease is characterized by the formation of immune complexes that deposit in tissues, leading to type III hypersensitivity reactions?

    <p>Systemic Lupus Erythematosus</p> Signup and view all the answers

    In Systemic Lupus Erythematosus, what leads to chronic disease setting and eventual tissue destruction?

    <p>Epitope spreading</p> Signup and view all the answers

    What process in SLE results in the production of broad Ig responses against various self-antigens?

    <p>Isotype switching of GC B cells</p> Signup and view all the answers

    What is the key factor that leads to T cell activation and epitope spreading in Systemic Lupus Erythematosus?

    <p>Defective apoptotic body clearance</p> Signup and view all the answers

    Which cells are primarily involved in capturing haptenated proteins during the sensitization stage of Contact Hypersensitivity?

    <p>Langerhans cells and cutaneous dendritic cells</p> Signup and view all the answers

    What is the effect of Fas ligand engagement with Fas in Contact Hypersensitivity?

    <p>Induces apoptosis of keratinocytes</p> Signup and view all the answers

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