OIA1010 HYPERSENSITIVITY I, II, III, IV

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40 Terms

1
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What is hypersensitivity?

An exaggerated or inappropriate immune response causing tissue damage or death.

2
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Who classified the types of hypersensitivity?

Coombs and Gell.

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What are the four types of hypersensitivity?

Type I (immediate), Type II (antibody-dependent), Type III (immune complex-mediated), and Type IV (cell-mediated).

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What mediates Type I hypersensitivity?

IgE antibodies binding to mast cells and basophils.

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Name common examples of Type I hypersensitivity.

Allergic asthma, hay fever, anaphylaxis, and urticaria (hives).

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What are the three phases of a Type I reaction?

Sensitization phase, reaction phase, and effector phase.

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What triggers mast cell degranulation in Type I hypersensitivity?

Cross-linking of IgE bound to allergens on mast cells.

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What are treatments for Type I hypersensitivity?

Epinephrine, antihistamines, corticosteroids, and allergen avoidance.

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What antibodies mediate Type II hypersensitivity?

IgG and IgM.

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How does complement activation contribute to Type II reactions?

It leads to cell lysis or opsonization for phagocytosis

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Name three examples of Type II hypersensitivity.

Hemolytic anemia, granulocytopenia, and thrombocytopenia.

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What is antibody-dependent cell-mediated cytotoxicity (ADCC)?

Destruction of IgG-coated target cells by NK cells or macrophages.

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What diagnostic test can confirm Type II hypersensitivity?

Detection of tissue-specific antibodies and complement deposition via immunofluorescence

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What mediates Type III hypersensitivity?

Soluble antigen-antibody immune complexes

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What role does complement play in Type III hypersensitivity?

It attracts neutrophils, which release lysosomal enzymes causing tissue damage.

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Give examples of diseases caused by Type III hypersensitivity.

Serum sickness, systemic lupus erythematosus (SLE), and Arthus reaction.

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What is the Arthus reaction?

A localized immune complex-mediated inflammatory reaction caused by antigen-antibody deposition.

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Why do neutrophils fail to clear immune complexes in Type III hypersensitivity?

Large immune complexes are difficult to phagocytose, leading to degranulation and tissue damage.

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What mediates Type IV hypersensitivity?

T lymphocytes, especially CD4+ and CD8+ cells.

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Why is Type IV hypersensitivity called delayed hypersensitivity?

It develops 24–72 hours after antigen exposure.

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What are two types of Type IV hypersensitivity?

Contact hypersensitivity and tuberculin-type hypersensitivit

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What are common causes of contact hypersensitivity?

Poison ivy, nickel, and certain drugs like sulfonamides.

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What does a positive tuberculin skin test indicate?

Previous exposure to Mycobacterium tuberculosis, not necessarily active disease.

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How do immune complexes in Type III hypersensitivity cause tissue damage?

By activating complement, leading to inflammation and neutrophil-mediated damage.

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What causes mast cell degranulation in Type I hypersensitivity?

Increased intracellular calcium triggered by IgE cross-linking.

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What is the main effector cell in Type IV hypersensitivity?

Macrophages activated by T cells.

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What distinguishes Type II from Type IIMacrophages activated by T cells.I hypersensitivity?

Type II targets cell surfaces, while Type III involves soluble immune complexes deposited in tissues.

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What role do cytokines play in Type IV hypersensitivity?

They recruit and activate macrophages and other inflammatory cells.

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What are the symptoms of anaphylaxis in Type I hypersensitivity?

Airway obstruction, hypotension, urticaria, and possible death.

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How does serum sickness manifest in Type III hypersensitivity?

Fever, rash, joint pain, and kidney damage due to immune complex deposition.

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What skin changes occur in contact dermatitis (Type IV)?

0Erythema, eczema, and necrosis within 12–48 hours.

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What causes hemolytic anemia in Type II hypersensitivity?

Antibodies binding to red blood cells, leading to complement-mediated lysis.

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How is Type I hypersensitivity managed?

With epinephrine, antihistamines, corticosteroids, and environmental interventions.

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What is the treatment for immune complex diseases?

Immunosuppressive drugs and removal of the antigen.

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Why is corticosteroid therapy useful in hypersensitivity?

It suppresses inflammation by inhibiting cytokine production.

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How are contact hypersensitivities diagnosed?

Through patch testing to identify allergens.

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What precautions should be taken for individuals prone to anaphylaxis?

Carrying an epinephrine auto-injector and avoiding known allergens.

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What diagnostic test is used for Type IV hypersensitivity?

Tuberculin skin test.

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What is a key diagnostic feature of Type II hypersensitivity?

Detection of autoantibodies and complement deposition in tissues.

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How is the wheal-and-flare reaction related to Type I hypersensitivity?

It is a hallmark of allergic reactions, caused by vasodilation and increased vascular permeability.