Block 9 Hypersensitivity MCQ's

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Block 9 Hypersensitivity MCQs - Quiz


Questions and Answers
  • 1. 

    Regarding anaphylactic (type I) and immune complex (type III) hypersensitivities, which of the following is the MOST accurate?

    • A.

      IgE is involved in both anaphylactic and immune complex hypersensitivibes

    • B.

      Complement is involved in both anaphylactic and immune complex hypersensitivities

    • C.

      Less antigen is typically needed to trigger and anaphylactic reaction than an immune complex reaction

    • D.

      Neutrophils play more important role in anaphylactic reactions than in immune complex reactions

    Correct Answer
    C. Less antigen is typically needed to trigger and anapHylactic reaction than an immune complex reaction
    Explanation
    In anaphylactic (type I) hypersensitivity, the immune system overreacts to an allergen, leading to the release of histamine and other chemicals that cause an immediate allergic reaction. This type of hypersensitivity is mediated by IgE antibodies. On the other hand, immune complex (type III) hypersensitivity occurs when antigen-antibody complexes deposit in tissues, leading to inflammation and tissue damage. Complement, a group of proteins involved in the immune response, is involved in both types of hypersensitivity reactions. However, the statement that less antigen is typically needed to trigger an anaphylactic reaction than an immune complex reaction is the most accurate. Anaphylactic reactions can occur with minimal exposure to an allergen, while immune complex reactions typically require a higher antigen load.

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  • 2. 

    A patient was undergoing a series of surgical procedures requiring general anesthetic. At the third procedure he suddenly became hypotensive with marked cardiac arrhythmia. In addition his breathing became difficuft due to extensive bronchocorstriction and obstructive laryngeal edema. Despite the efforts of the surgical team the patient developed severe and permanent brain damage due to hypoxernia. It was subsequently discovered that the patient had developed IgG antibodies to the anesthetic gas and this had resulted in an anaphylactoid response to the anesthetic. What type of reaction caused this condition?

    • A.

      Type I Hypersensitivity

    • B.

      Type II Hypersensitivity

    • C.

      Type III Hypersensitivity

    • D.

      Type IV Hypersensitivity

    • E.

      Direct activation of mast cells by the anesthetic gas

    Correct Answer
    C. Type III Hypersensitivity
    Explanation
    not type I b/c no IgE
    not type II b/c the antigen is not membrane bound

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  • 3. 

    Leprosy is a chronic infectious disease caused by Mycobacterium leprae. The ability of this organism to cause disease is related to it’s ability to infect, persist  in, and replicate within macrophages. The lepromin skin test is used to determine what type of leprosy a person has. In this test, inactivated Mycobacterium leprae organisms are injected just beneath the skin. At the site of injection, a person with a positive test will develop an area of induration with erythema peaking around 48 hours after the injection. If this test measures a hypersensitivity reaction against the organism, what type of hypersensitivity reaction is it intended to detect?

    • A.

      Type I

    • B.

      Type IV

    • C.

      Type II

    • D.

      Type II or III

    • E.

      Type III

    Correct Answer
    B. Type IV
    Explanation
    The lepromin skin test is intended to detect a Type IV hypersensitivity reaction. Type IV hypersensitivity is also known as delayed-type hypersensitivity (DTH) and is mediated by T cells and macrophages. In this test, inactivated Mycobacterium leprae organisms are injected, and if a person has a positive test, they will develop an area of induration with erythema after 48 hours. This reaction indicates a delayed immune response against the organism, which is characteristic of a Type IV hypersensitivity reaction.

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  • 4. 

    The principle difference between type II and type III hypersensitivity is:

    • A.

      The class (isotype of antibody)

    • B.

      Whether the antibody reacts with the antigen on the cell or reacts with antigen before it interacts with the cell

    • C.

      The participation of complement

    • D.

      The participation of T cells

    Correct Answer
    B. Whether the antibody reacts with the antigen on the cell or reacts with antigen before it interacts with the cell
    Explanation
    IN TYPE II HYPERSENSITIVITY-- (or cytotoxic hypersensitivity) the antibodies produced by the immune response bind to antigens on the patient's own cell surfaces. The antigens recognized in this way may either be intrinsic ("self" antigen, innately part of the patient's cells) or extrinsic (adsorbed onto the cells during exposure to some foreign antigen, possibly as part of infection with a pathogen). These cells are recognized by macrophages or dendritic cells, which act as antigen-presenting cells. This causes a B cell response, wherein antibodies are produced against the foreign antigen.
    An example of type II hypersensitivity is the reaction to penicillin wherein the drug can bind to red blood cells, causing them to be recognized as different; B cell proliferation will take place and antibodies to the drug are produced. IgG and IgM antibodies bind to these antigens to form complexes that activate the classical pathway of complement activation to eliminate cells presenting foreign antigens (which are usually, but not in this case, pathogens). That is, mediators of acute inflammation are generated at the site and membrane attack complexes cause cell lysis and death. The reaction takes hours to a day.
    Another form of type II hypersensitivity is called antibody-dependent cell-mediated cytotoxicity (ADCC). Here, cells exhibiting the foreign antigen are tagged with antibodies (IgG or IgM). These tagged cells are then recognised by natural killer (NK) cells and macrophages (recognised via IgG bound (via the Fc region) to the effector cell surface receptor, CD16 (FcγRIII)), which in turn kill these tagged cells.
    TYPE III HYPERSENSITIVITY --occurs when antigens and antibodies (IgG or IgM) are present in roughly equal amounts, causing extensive cross-linking.
    Presentation
    Type III hypersensitivity occurs when there is little antibody and an excess of antigen, leading to small immune complexes being formed that do not fix complement and are not cleared from the circulation. It is characterized by solvent antigens that are not bound to cell surfaces (which is the case in type II hypersensitivity). When these antigens bind antibodies, immune complexes of different sizes form. Large complexes can be cleared by macrophages but, comparatively macrophages have difficulty in the disposal of small immune complexes. These immune complexes insert themselves into small blood vessels, joints, and glomeruli, causing symptoms. Unlike the free variant, a small immune complex bound to sites of deposition (like blood vessel walls) are far more capable of interacting with complement; these medium-sized complexes, formed in the slight excess of antigen, are viewed as being highly pathogenic.
    Such depositions in tissues often induce an inflammatory response, and can cause damage wherever they precipitate. The cause of damage is as a result of the action of cleaved complement anaphylotoxins C3a and C5a, which, respectively, mediate the induction of granule release from mast cells (from which histamine can cause urticaria), and recruitment of inflammatory cells into the tissue (mainly those with lysosomal action, leading to tissue damage through frustrated phagocytosis by PMNs and macrophages)
    The reaction can take hours, days, or even weeks to develop, depending on whether or not there is immunlogic memory of the precipitating antigen. Typically, clinical features emerge a week following initial antigen challenge, when the deposited immune complexes can precipitate an inflammatory response. Because of the nature of the antibody aggregation, tissues that are associated with blood filtration at considerable osmotic and hydrostatic gradient (e.g. sites of urinary and synovial fluid formation, kidney glomeruli and joint tissues respectively) bear the brunt of the damage. Hence, vasculitis, glomerulonephritis and arthritis are commonly-associated conditions as a result of type III hypersensitivity responses
    As observed under methods of histopathology, acute necrotizing vasculitis within the affected tissues is observed concomitant to neutrophilic infiltration, along with notable eosinophilic deposition (FIBRINOID NECROSIS). Often, immunofluorescence microscopy can be used to visualize the immune complexes. Skin response to a hypersensitivity of this type is referred to as an ARTHUS REACTION, and is characterized by local erythema and some induration. Platelet aggregation, especially in microvasculature, can cause localized clot formation, leading to blotchy hemorrhages. This typifies the response to injection of foreign antigen sufficient to lead to the condition of SERUM SICKNESS

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  • 5. 

    A child stung by a bee experiences respiratory distress within minutes and lapses into unconsciousness. This reaction is probably mediated by:

    • A.

      IgE antibody

    • B.

      IgG antibody

    • C.

      Sensitized T cells

    • D.

      Complement

    • E.

      IgM antibody

    Correct Answer
    A. IgE antibody
    Explanation
    The correct answer is IgE antibody. When a child is stung by a bee, the immune system may produce IgE antibodies in response to the bee venom. These IgE antibodies bind to mast cells and basophils, triggering the release of inflammatory mediators such as histamine. This can lead to respiratory distress and unconsciousness, which are characteristic of an allergic reaction. IgG antibodies, sensitized T cells, complement, and IgM antibodies are not typically involved in this type of immediate hypersensitivity reaction.

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  • 6. 

    A patient with severe asthma gets no relief from antihistamines. The symptoms are MOST likely to be caused by:

    • A.

      IL-2

    • B.

      Leukotrienes

    • C.

      Serotonin

    • D.

      Bradykinin

    Correct Answer
    B. Leukotrienes
    Explanation
    Leukotrienes are the most likely cause of the severe asthma symptoms in this patient. Leukotrienes are inflammatory molecules released by immune cells in response to triggers like allergens. They cause bronchoconstriction, mucus production, and inflammation in the airways, leading to asthma symptoms. Antihistamines, on the other hand, primarily target histamine, which is involved in allergic reactions but not as strongly linked to asthma symptoms as leukotrienes. IL-2, serotonin, and bradykinin are not typically associated with asthma symptoms.

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  • 7. 

    Hypersensitivity to penicillin and hypersensitivity to poison oak are both:

    • A.

      Mediated by IgE antibody

    • B.

      Mediated by IgG and IgM antibody

    • C.

      Intiated by haptens

    • D.

      Initiated by Th2 cells

    Correct Answer
    C. Intiated by haptens
    Explanation
    Hypersensitivity to penicillin and hypersensitivity to poison oak are both initiated by haptens. Haptens are small molecules that can bind to larger molecules in the body, forming a complex that is recognized as foreign by the immune system. This triggers an immune response, leading to hypersensitivity reactions. In the case of penicillin, the hapten is the penicillin molecule itself, while in the case of poison oak, the hapten is a chemical called urushiol found in the plant. These haptens can bind to proteins in the body, forming haptens-protein complexes that activate the immune system and cause hypersensitivity reactions.

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  • 8. 

    Your patient has been treated for endocarditis with Penicillin G for the past 2 weeks. She now has fever and maculopapular erythematous rash over her chest and abdomen. A urinalysis shows significant protein in the urine. If the fever, rash and proteinuria are immunologic in origin, which one of the following is MOST likely to be involved?

    • A.

      IgG and complement

    • B.

      IgE and histamine

    • C.

      IL-2 and cytotoxic T cells

    • D.

      Gamma interferon and macrophages

    Correct Answer
    A. IgG and complement
    Explanation
    The patient's symptoms of fever, rash, and proteinuria are suggestive of an immune-mediated reaction. IgG and complement are involved in type III hypersensitivity reactions, which can cause a maculopapular rash and glomerulonephritis with proteinuria. IgE and histamine are involved in type I hypersensitivity reactions, which typically present with urticaria and not proteinuria. IL-2 and cytotoxic T cells are involved in cell-mediated immune responses, which do not typically cause rash and proteinuria. Gamma interferon and macrophages are involved in type II hypersensitivity reactions, which are not associated with the symptoms described.

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  • 9. 

    A child disturbs a wasp nest, is stung repeatedly, and goes into shock within minutes, manifesting respiratory failure and vascular collapse. This is MOST likely due to;

    • A.

      Systemic anaphylaxis

    • B.

      Serum sickness

    • C.

      An Arthus reaction

    • D.

      Cytotoxic hypersensitivity

    Correct Answer
    A. Systemic anapHylaxis
    Explanation
    Serum sickness, and Arthurs reaction are Type III

    In type II hypersensitivity (or cytotoxic hypersensitivity) the antibodies produced by the immune response bind to antigens on the patient's own cell surfaces.

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  • 10. 

    A delayed hypersensitivity reaction is characterized by:

    • A.

      Edema without a cellular infiltrate

    • B.

      An infiltrate composed of neutrophiis

    • C.

      An infiltrate composed of helper T cells and macrophages

    • D.

      An infiltrate composed of eosinophils

    Correct Answer
    C. An infiltrate composed of helper T cells and macropHages
    Explanation
    DTH is type 4, which involves Tcells, macrophages IFN-g and TNF-a

    Type IV hypersensitivity is often called Delayed Type Hypersensitivity as the reaction takes two to three days to develop. Unlike the other types, it is not antibody mediated but rather is a type of cell-mediated response.

    CD4+ helper T cells recognize antigen in a complex with either type 1 or 2 major histocompatibility complex. The antigen-presenting cells in this case are macrophages that secrete IL-12, which stimulates the proliferation of further CD4+ T cells. CD4+ T cells secrete IL-2 and interferon gamma, further inducing the release of other Type 1 cytokines, thus mediating the immune response. Activated CD8+ T cells destroy target cells on contact, whereas activated macrophages produce hydrolytic enzymes and, on presentation with certain intracellular pathogens, transform into multinucleated giant cells.

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  • 11. 

    In Henoch-Schonlein purpura, what is the reason for the purpuric rash?

    • A.

      Bacteria that adhere to vascular walls inducing necrosis

    • B.

      IgM immune complexes that induce vasculitis

    • C.

      Immune-mediated destruction of bacteria, releasing endotoxin

    • D.

      The disease is a the result of superantigen activity by the infectious agent

    • E.

      IgA immune complexes that induce vasculitis

    Correct Answer
    E. IgA immune complexes that induce vasculitis
    Explanation
    it is a type 3 rxn which usually involves IgM, but Henoch-Schonlein is an exception that involves IgA.

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  • 12. 

    A 44-year-old man is given an intramuscular high dose of penicillin. About 8 days later, he develops chills, fever and a rash, If his symptoms are due to an immune reaction to the drug, what type of reaction is this considered?

    • A.

      Type I Hypersensitivity reaction

    • B.

      Type II Hypersensitivity reaction

    • C.

      Type IV Hypersensitivity reaction

    • D.

      Anaphylactoid reaction

    • E.

      Type III Hypersensitivity reaction

    Correct Answer
    E. Type III Hypersensitivity reaction
    Explanation
    This reaction is considered a Type III Hypersensitivity reaction because it occurs 8 days after the administration of the drug, which is consistent with the time frame for a Type III reaction. In Type III reactions, immune complexes are formed between the drug and antibodies, which then deposit in tissues and activate complement. This can lead to the symptoms of chills, fever, and rash seen in the patient.

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Our quizzes are rigorously reviewed, monitored and continuously updated by our expert board to maintain accuracy, relevance, and timeliness.

  • Current Version
  • Apr 24, 2023
    Quiz Edited by
    ProProfs Editorial Team
  • May 05, 2012
    Quiz Created by
    Chachelly
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