Micro Hypersensitiviy Dr Sloma

1.

. 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
The principle difference between type II and type III hypersensitivity is whether the antibody reacts with the antigen on the cell or reacts with the antigen before it interacts with the cell. In type II hypersensitivity, the antibody binds to antigens on the surface of cells, leading to cell destruction. In type III hypersensitivity, the antibody forms immune complexes with soluble antigens before depositing in tissues, causing inflammation and tissue damage. The other options, such as the class of antibody, the participation of complement, and the participation of T cells, may also play a role in the immune response but do not differentiate between type II and type III hypersensitivity.

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2.

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
When a child is stung by a bee, the body's immune system may produce an excessive amount of IgE antibodies in response to the bee venom. IgE antibodies are responsible for triggering an allergic reaction, which can cause respiratory distress and unconsciousness. This is known as anaphylaxis and is a severe allergic reaction. Therefore, the correct answer is IgE antibody.

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3.

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, particularly mast cells, in response to allergens or other triggers. They cause bronchoconstriction, increased mucus production, and inflammation in the airways, leading to asthma symptoms. Antihistamines primarily target histamine, which is involved in allergic reactions but not as directly implicated in asthma symptoms as leukotrienes. IL-2, serotonin, and bradykinin are not typically associated with asthma symptoms.

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4.

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 proteins in the body, forming a complex. This complex triggers an immune response, leading to hypersensitivity reactions. In the case of penicillin, the hapten is the penicillin molecule itself, while in poison oak, the hapten is urushiol, a chemical found in the plant. These haptens can bind to proteins in the body and trigger an immune response, resulting in allergic reactions.

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5.

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 histimine
C.

IL-2 and cytotoxic T cells
D.

Gamma interferon and macrophages

Correct Answer
A. IgG and complement

Explanation
So the patient’s symptoms start 2 weeks after the she starts taking the drug, so this suggests that the symptoms are not due to type I hypersensitivity. The time line corresponds with the formation of antibodies against the drug. Type II and type III hypersensitivity reactions can causes a rash like the one described and can also result the kidney damage that the patient is experiencing. Both type II and type III hypersensitivity are mediated by IgG antibodies triggering activation of complement.

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6.

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 (Some references refer to type II hypersensitivity as “cytotoxic hypersensitivity”)

Correct Answer
A. Systemic anapHylaxis

Explanation
The child's symptoms of respiratory failure and vascular collapse within minutes after being stung repeatedly by wasps suggest a severe and rapid allergic reaction known as systemic anaphylaxis. Systemic anaphylaxis occurs when the immune system overreacts to an allergen, in this case, the wasp venom. This leads to the release of large amounts of histamine and other chemicals, causing widespread inflammation and constriction of blood vessels. The symptoms of shock, respiratory failure, and vascular collapse are characteristic of systemic anaphylaxis.

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7.

Reaction to poison ivy or poison oak is:

A.

An-IgG mediated response
B.

An IgE-mediated response
C.

A cell-mediated response
D.

An Arthus reaction

Correct Answer
C. A cell-mediated response

Explanation
The correct answer is a cell-mediated response. When exposed to poison ivy or poison oak, the body's immune system reacts by activating T-cells, which are a type of white blood cell. These T-cells release chemicals that cause inflammation and initiate the immune response. This response is not mediated by antibodies like IgG or IgE, but rather by the direct action of immune cells. This type of response is known as a cell-mediated response.

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8.

A delayed hypersensitivity reaction is characterized by:

A.

Edema without a cellular infiltrate
B.

An infiltrate composed of neutrophils
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
A delayed hypersensitivity reaction is characterized by an infiltrate composed of helper T cells and macrophages. This type of reaction is a delayed immune response that occurs hours to days after exposure to an antigen. Helper T cells play a crucial role in coordinating the immune response and activating macrophages to eliminate the antigen. Therefore, the presence of helper T cells and macrophages in the infiltrate is indicative of a delayed hypersensitivity reaction.

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9.

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 hypersensitivities
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, IgE antibodies are involved in the immune response. These antibodies bind to mast cells and basophils, causing the release of inflammatory mediators such as histamine. On the other hand, immune complex (type III) hypersensitivity involves the formation of antigen-antibody complexes that deposit in tissues, leading to inflammation and tissue damage. Complement proteins are involved in the activation of the inflammatory response 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 be triggered by small amounts of allergens, while immune complex reactions usually require a larger amount of antigen to form immune complexes.

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