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DEN 2027 - Disease Mechanisms > Hypersensitivity > Flashcards

Hypersensitivity Flashcards

1
Q

What is hypersensitivity?

A

Exaggerated or inappropriate immune response

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2
Q

What 3 things can hypersensitivity lead to?

A
  1. Tissue damage
  2. Serious disease
  3. Death
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3
Q

Give an example of hypersensitivity reactions

A

Anaphylaxis

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4
Q

What is angioedema in anaphylaxis?

A

A person is unable to breathe so oxygen has to be provided by a tube

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5
Q

Name 4 types of hypersensitivity reactions?

A
  1. Type I - IgE mediated
  2. Type II - Cytolytic or cytotoxic
  3. Type III - Immune complex
  4. Type IV - Cell mediated immunity
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6
Q

What are 2 main differences between type 1, type 2 and type 3 hypersensitivity reactions and type 4 hypersensitivity reactions?

A
  1. Type 1, type 2 and type 3 hypersensitivity reactions are mediated by antibodies and type 4 hypersensitivity reactions are mediated by T-cells
  2. Type 1, type 2 and type 3 hypersensitivity reactions are immediate and type 4 hypersensitivity reactions are delayed
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7
Q

What are the 3 phases of Type I Hypersensitivity?

A
  1. Sensitisation
  2. Activation
  3. Effector
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8
Q

What occurs during the sensitisation phase of Type I Hypersensitivity?

A
  • Exposure to allergen activated Th2 cells which stimulate B cells to form IgE producing plasma cells
  • IgE produced binds to Fc receptors on mast cells and basophils
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9
Q

What occurs during the activation phase of Type I Hypersensitivity?

A

Re-exposure to antigen triggers mast cells and basophils to response by release of granules

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10
Q

What occurs during the effector phase of Type I Hypersensitivity?

A

Complex response occurs as a result of histamine and other active agents released by mast cells and basophils

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11
Q

What are 5 effects of the effector phase on the body during Type I Hypersensitivity?

A
  1. Contraction of bronchial smooth muscles
  2. Increase mucus secretion
  3. Increased permeability of venules due to contraction of endothelial cells
  4. Vasodilation
  5. Stimulation of nerve endings
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12
Q

Name 3 physical expressions of effectors during Type I Hypersensitivity

A
  1. Airways obstructed
  2. Drop in blood pressure
  3. Cough
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13
Q

How quickly does Type I Hypersensitivity occur from exposure?

A

Immediate

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14
Q

Name 4 examples of localised Type I Hypersensitivity

A
  1. Hay fever (allergic rhinitis)
  2. Food allergy
  3. Atopic dermatitis
  4. Asthma
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15
Q

What is systemic anaphylaxis?

A

Shock-like and often fatal state initiated by an allergen introduced into the blood or absorbed by the gut or skin

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16
Q

Name 4 things which can cause systemic anaphylaxis

A
  1. Nuts
  2. Insulin
  3. Seafood
  4. Venom from bees, wasps or ants
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17
Q

What is the treatment for systemic anaphylaxis?

A

Epinephrine

18
Q

What are the 3 main types of treatment available for Type I Hypersensitivity reactions?

A
  1. Environmental
  2. Pharmacologic
  3. Immunological
19
Q

Name 5 pharmacologic treatments for Type I Hypersensitivity reactions

A
  1. Antihistamines
  2. Cromolyn chloride
  3. Corticosteroids
  4. Theophylline
  5. Epinephrine
20
Q

Name 2 immunological treatments for Type I Hypersensitivity reactions

A
  1. Desensitization

2. Humanized anti-IgE antibodies

21
Q

How does Type II Hypersensitivity work?

A

Antibody bound to cell surface antigen activates complement system or mediates cell destruction by antibody-dependent cell mediated cytotoxicity (ADCC)

22
Q

What two antibodies can mediate Type II Hypersensitivity?

A
  1. IgG

2. IgM

23
Q

What is the main example of Type II Hypersensitivity?

A

Blood transfusion reactions

24
Q

How does Th2 cells cause B cells to divide?

A

It produces IL-4 which causes the B cells to become plasma cells by class switching

25
Q

What 3 reactions can be caused if incorrect blood transfusion?

A
  1. Intravascular haemolysis
  2. Increased hemoglobulin filtered through in kidneys
  3. Hemoglobulin converted to toxic bilirubin
26
Q

What are 5 physical symptoms of an incorrect blood transfusion?

A
  1. Fever
  2. Chills
  3. Nausea
  4. Lower back pain
  5. Blood clotting
27
Q

Name 3 common sites of Type III Hypersensitivity reactions?

A
  1. Blood vessel walls
  2. Synovial membrane in joints
  3. Glomerular basement membrane of kidney
28
Q

What occurs during the deposition of complexes?

A

Recruitment of neutrophils to the site, where lytic enzymes from granular release causes tissue damage

29
Q

What facilitates the movement of neutrophils to site of complexes?

A

Compliment proteins produced by the complexes

30
Q

Why are lytic enzymes released as opposed to phagocytosis occuring?

A

Neutrophils are hyper activated as they cannot take up larger immune complexes

31
Q

Name 3 types of Type III Hypersensitivity reactions

A
  1. Farmers lung
  2. Pigeons fancier’s disease
  3. Serum sickness
32
Q

What is a Type IV Hypersensitivity reaction?

A

Localized inflammatory response induced by Th cells

33
Q

What characterises a Type IV Hypersensitivity reaction?

A

A large influx of inflammatory cells and macrophages

34
Q

Why are Type IV Hypersensitivity reactions important?

A

Important in defence against parasites and bacteria which live within cells

35
Q

Give 5 examples of pathogens associated with Type IV Hypersensitivity

A
  1. Mycobacterium tuberculosis
  2. Mycobacterium leprae
  3. Candida albicans
  4. Herpes simplex
  5. Measles
36
Q

What are Langerhans cells?

A

Immune cells found in the spleen

37
Q

What occurs during Type IV Hypersensitivity reactions?

A
  • Antigen presenting cells activate Th1 cells
  • Th1 cells cause release of cytokines and chemokines which attract macrophages
  • Activated macrophage increase MCH class II expression to amplify Th1 response
38
Q

What are 4 effects of macrophage effect during Type IV Hypersensitivity?

A
  1. MHC class II expression increased
  2. TNF receptors increased
  3. Oxygen radicals increased
  4. Nitric oxide increased
39
Q

What can occur if there is a prolonged DTH response?

A

Formation of granulomas due to continuous activation of macrophages

40
Q

Name the 5 steps during the continuous activation of macrophages to cause tissue damage

A
  1. Macrophages are hyper activated so adhere to each other
  2. Fuse to form granulomas
  3. Form palpable nodules
  4. Release lytic enzymes
  5. Tissue damage
41
Q

What is an example of prolonged DHT response?

A

Mycobacterium tuberculosis in the lung

42
Q

Describe the stages of contact dermatitis

A
  • Antigen in poison ivy oil penetrates skin
  • Forms covalent bonds with proteins
  • Proteins taken up by Langerhans cells and macrophages
  • Antigenic peptides presented via MHC class II to Th1 cells
  • Th1 induces immune response
  • Recruitment of activated macrophages to site of inflammation and release of lytic enzymes

DEN 2027 - Disease Mechanisms (20 decks)

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