Harmful Immune Responses and Hypersensitivity Reactions
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Questions and Answers

Which type of hypersensitivity reaction is solely mediated by cells and not antibodies?

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

    • What is the main immunoglobulin involved in a type I hypersensitivity reaction?

  • IgG
  • IgA
  • IgM
  • IgE (correct)

    • What chemical mediator is released during the degranulation of mast cells in anaphylactic reactions?

  • Interleukin
  • Histamine (correct)
  • Complement proteins
  • Antibodies

    • Which clinical type of type I hypersensitivity is characterized by hypotension and shock?

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

    Which allergen is not typically associated with atopy?

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

    What happens during the sensitizing dose in a type I hypersensitivity reaction?

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

    Which of the following is a genetically based local form of type I hypersensitivity?

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

    Which of the mechanisms below is involved in the shocking dose of a type I hypersensitivity reaction?

    <p>Degranulation of mast cells and release of mediators</p> Signup and view all the answers

    Which of the following immunoglobulins are involved in Type II cytolytic reactions?

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

    How does an antibody react in a Type II cytolytic reaction?

    <p>By reacting with antigens on the cell surface</p> Signup and view all the answers

    What role does the complement system play in Type II reactions?

    <p>Formation of the membrane attack complex (MAC)</p> Signup and view all the answers

    What initiates the formation of micro thrombi in Type III toxic complex syndrome?

    <p>Release of lysosomal enzymes</p> Signup and view all the answers

    Which cells are primarily involved in Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC) in Type II reactions?

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

    What is the result of the formation of micro precipitates in Type III reactions?

    <p>Inflammation and possible mechanical blockage</p> Signup and view all the answers

    What triggers the immune response in type II hypersensitivity?

    <p>Binding of immunoglobulins to antigens on cell membranes</p> Signup and view all the answers

    Which type of hypersensitivity is primarily associated with transfusion reactions due to ABO incompatibility?

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

    Which of the following processes does not occur in toxic complex syndrome (Type III hypersensitivity)?

    <p>Binding of immunoglobulins to cell surfaces</p> Signup and view all the answers

    Which hypersensitivity reaction is described as cell-mediated and delayed?

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

    Which clinical condition is an example of type II hypersensitivity involving autoimmune disease?

    <p>Hashimoto's thyroiditis</p> Signup and view all the answers

    What role do neutrophils play in toxic complex syndrome?

    <p>They phagocytose immune complexes and release lysosomal enzymes</p> Signup and view all the answers

    Which clinical form of type I hypersensitivity reaction may result in death within 20 minutes?

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

    What is a common inhalant allergen that can cause type I hypersensitivity reactions?

    <p>House dust</p> Signup and view all the answers

    Which drug reaction is a cause for type II hypersensitivity leading to thrombocytopenia?

    <p>a-methyl dopa</p> Signup and view all the answers

    Which type of hypersensitivity reaction is systemic and can manifest by hypotension, shock, and respiratory distress?

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

    What type of allergic reaction would likely occur if the antigen-antibody reaction happens in the bronchi?

    <p>Bronchial asthma</p> Signup and view all the answers

    Which of the following is NOT a common cause of anaphylaxis?

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

    The term 'atopy' refers to which of the following?

    <p>Local form of type I hypersensitivity reaction</p> Signup and view all the answers

    Which symptom is least likely to be caused by a local type I hypersensitivity reaction in the gastrointestinal tract?

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

    What clinical condition is characterized by a local immune complex deposition resulting in erythema, edema, and necrosis after repeated injections?

    <p>Arthus reaction</p> Signup and view all the answers

    Which type of graft occurs between genetically identical twins?

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

    What is a common clinical presentation of serum sickness?

    <p>Fever, urticaria, and arthralgia</p> Signup and view all the answers

    What hypersensitivity reaction is initiated by intracellular organisms like bacteria and pathogenic fungi?

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

    Which of the following is an example of a delayed hypersensitivity skin test?

    <p>Tuberculin test</p> Signup and view all the answers

    Which of the following conditions is associated with systemic lupus erythematosus and rheumatoid arthritis?

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

    What clinical signs are indicative of contact dermatitis?

    <p>Redness, swelling, vesicles, scaling, and crusting</p> Signup and view all the answers

    In which type of hypersensitivity reaction do sensitized Th cells release cytokines that attract and activate macrophages, causing an inflammatory response?

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

    What are the symptoms of Graft Versus Host Reaction (GVHR)?

    <p>Fever, pancytopenia, rash, hepatosplenomegaly, diarrhea and death</p> Signup and view all the answers

    Which of the following methods is not used in the prevention of graft rejection?

    <p>Choosing a donor with mismatched HLA typing</p> Signup and view all the answers

    What is required to maintain immunological tolerance?

    <p>Persistence of antigen</p> Signup and view all the answers

    Which of the following is true about immunological tolerance?

    <p>Tolerance can be naturally broken</p> Signup and view all the answers

    What does the prevention method of post-operative immunosuppression involve?

    <p>Use of anti-CD3 antibodies and immunosuppressive drugs</p> Signup and view all the answers

    Which characteristic best defines immunological autotolerance?

    <p>Non-reactivity to self antigens</p> Signup and view all the answers

    Which cells release cytokines during the inflammatory reaction in delayed hypersensitivity?

    <p>Sensitized Th cells</p> Signup and view all the answers

    Which test involves the intradermal injection of a purified protein derivative (PPD) to check for delayed hypersensitivity?

    <p>Tuberculin test</p> Signup and view all the answers

    What type of graft involves transplantation between two genetically identical individuals?

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

    Which type of hypersensitivity reaction is delayed and does not involve antibodies?

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

    What typically causes the clinical signs of contact dermatitis?

    <p>Chemical substances</p> Signup and view all the answers

    Which cells accumulate at the site of injection during a positive tuberculin skin test?

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

    What happens when sensitized Th cells recognize a specific antigen in delayed hypersensitivity?

    <p>They activate and release cytokines</p> Signup and view all the answers

    Which of the following is a characteristic clinical sign of contact dermatitis?

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

    What can result in 'immune paralysis'?

    <p>Very high and very low doses of antigens</p> Signup and view all the answers

    Which drug is associated with type II hypersensitivity when binding to R.B.Cs?

    <p>Alpha methyl dopa (Aldomet)</p> Signup and view all the answers

    What is a common result of microbial antigens that cross-react with self antigens?

    <p>Rheumatic fever</p> Signup and view all the answers

    Which autoimmune condition is associated with an increased antibody formation to IgG?

    <p>Rheumatoid arthritis</p> Signup and view all the answers

    Which of the following HLA types is commonly associated with autoimmune diseases?

    <p>HLA-B8</p> Signup and view all the answers

    Which of the following is a method used for the treatment of autoimmune diseases?

    <p>Induction of tolerance</p> Signup and view all the answers

    Which mechanism can lead to the escape of autoreactive clones during immune cells development and maturation?

    <p>Clonal deletion</p> Signup and view all the answers

    What role do regulatory T cells play in autoimmunity?

    <p>Maintain autotolerance</p> Signup and view all the answers

    Which factor does NOT enhance tolerance?

    <p>Administration of cross-reacting antigens</p> Signup and view all the answers

    What is 'immune paralysis'?

    <p>A condition where high doses of purified polysaccharides or amino acid co-polymers suppress immune response</p> Signup and view all the answers

    Which autoimmune disease is characterized by the formation of autoantibodies and damage to self tissues?

    <p>Systemic lupus erythematosus</p> Signup and view all the answers

    Which theory explains the autoimmune response due to exposure to microbial antigens?

    <p>Molecular mimicry</p> Signup and view all the answers

    Which HLA gene association is NOT mentioned in the context of autoimmune diseases?

    <p>HLA-A1</p> Signup and view all the answers

    Which is NOT a treatment option for autoimmune diseases?

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

    Which of the following does NOT influence the induction of tolerance?

    <p>Hydration levels</p> Signup and view all the answers

    What is the result of a decrease in suppressor functions of the immune system?

    <p>Development of autoimmune diseases</p> Signup and view all the answers

    Which diagnostic marker is NOT associated with autoimmune diseases?

    <p>Increased insulin levels</p> Signup and view all the answers

    Which autoimmune disease is linked with hormone influences being more common in women?

    <p>Systemic lupus erythematosus</p> Signup and view all the answers

    What type of graft is an organ transplant between two humans?

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

    Which cells are directly responsible for destroying graft cells in cell-mediated graft rejection?

    <p>T cytotoxic (Tc) cells</p> Signup and view all the answers

    What is the main cause of hyperacute graft rejection?

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

    Which type of hypersensitivity is involved in antibody-dependent cellular cytotoxicity (ADCC) in graft rejection?

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

    Which condition occurs when immunocompetent bone marrow graft cells react against an immunocompromised recipient's tissues?

    <p>Graft versus host reaction (GVHR)</p> Signup and view all the answers

    How is maintenance of immune tolerance achieved?

    <p>Via irradiation and certain drugs</p> Signup and view all the answers

    Which of these hypersensitivity reactions involves immune complexes depositing on vessel walls and causing ischemia in grafts?

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

    Which factor is NOT considered a preventive measure against graft rejection?

    <p>Use of preformed antibodies before transplantation</p> Signup and view all the answers

    Study Notes

    Harmful Immune Responses

    • Inappropriate immune responses can lead to tissue damage due to:
      • Overactive immune response
      • Inappropriate recognition (autoimmune diseases)

    Hypersensitivity Reactions

    • Undesirable effects of the normal immune system following re-exposure to a harmless antigen in a genetically susceptible individual
    • Types:
      • Type I: Anaphylactic (Immediate) reaction
      • Type II: Cytolytic (Cytotoxic) reaction
      • Type III: Toxic complex syndrome
      • Type IV: Delayed hypersensitivity

    Type I Hypersensitivity

    • Mechanism:
      • IgE antibody fixes to mast cells and basophils
      • Antigen bridges between IgE molecules, causing degranulation and release of chemical mediators
    • Clinical types:
      • Anaphylaxis: systemic form, manifests as hypotension, shock, and respiratory distress
      • Atopy: local form, manifests depending on the site of antigen exposure (e.g. bronchial asthma, diarrhea, urticaria)

    Type II Hypersensitivity

    • Mechanism:
      • IgG or IgM antibody reacts with antigen on cell surface
      • Complement activation, opsonization, and ADCC
    • Clinical types:
      • Transfusion reactions
      • Autoimmune diseases (e.g. Hashimoto's thyroiditis)
      • Graft rejection

    Type III Hypersensitivity

    • Mechanism:
      • Combination of antigen and circulating antibody
      • Formation of micro-precipitates and inflammation
    • Clinical types:
      • Arthus reaction: local immune complex deposition
      • Serum sickness: systemic immune complex deposition
      • Post-streptococcal glomerulonephritis

    Type IV Hypersensitivity

    • Mechanism:
      • Sensitized T cells react with antigen
      • Release of cytokines and activation of macrophages and Tc cells
    • Clinical types:
      • Skin tests (e.g. tuberculin test)
      • Contact dermatitis

    Transplantation and Graft Rejection

    • Types of grafts:
      • Autograft: graft between 2 sites of the same individual
      • Isograft: graft between 2 genetically identical individuals
      • Allograft: graft between 2 genetically different individuals of the same species
      • Xenograft: graft between different species
    • Mechanisms of graft rejection:
      • Cell-mediated and humoral mechanisms
      • T helper and T cytotoxic cells, B cells, and antibody production
    • Types of graft rejection:
      • Hyperacute: occurs minutes to hours after transplantation
      • Acute: occurs 10-30 days after transplantation
      • Chronic: occurs months or years after transplantation

    Graft Versus Host Reaction (GVHR)

    • Occurs when an immunocompromised recipient receives an immunocompetent bone marrow graft
    • Grafted cells react against the host's tissues
    • Manifested by fever, pancytopenia, and death

    Tolerance

    • Specific immunological non-reactivity to an antigen
    • Can be induced by:
      • Irradiation
      • Certain drugs
      • Immunosuppressant therapy
    • Maintenance of tolerance requires persistence of antigen

    Autoimmune Diseases

    • Occur due to breakdown of mechanisms that maintain autotolerance
    • Examples: autoimmune haemolytic anaemia, Hashimoto's thyroiditis, systemic lupus erythematosus, ulcerative colitis, and rheumatoid arthritis
    • Theories:
      • Release of sequestered antigens
      • Alteration of self-antigens
      • Exposure to microbial antigens
      • Decrease in suppressor functions
      • Escape of autoreactive clone
      • Hormonal influences
    • Genetic predisposition:
      • Association between certain HLA genes and autoimmune diseases
    • Diagnosis:
      • Elevated serum level of autoantibodies and rheumatoid factors
      • Complement levels may be decreased
      • Immune complexes may be detected in serum
    • Treatment:
      • Anti-inflammatory drugs
      • Immunosuppressive drugs
      • Plasmapheresis
      • Anti-TNF and Abatacept
      • Induction of tolerance

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    Learn about the negative consequences of immune responses, including autoimmune diseases and hypersensitivity reactions, and their types.

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