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1.3 POM Immunology > Hypersensitivity > Flashcards

Hypersensitivity Flashcards

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1
Q

What is an antigen?

A

Substance that can stimulate an antibody response

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2
Q

What is an antibody?

A

Y shaped heterodimeric protein that binds to an antigen
- Immunoglobin
- BCR when bound to B cells

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3
Q

What is an adjuvant?

A

Substance enhancing immune response to an antigen

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4
Q

What is an allergen?

A

Anitgen/substance that stimulates an allergic reaction (type 1 hypersensitivity)

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5
Q

What is a hapten?

A

Molecule that can become antigenic when associated with a larger carrier protein

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6
Q

What is hypersensitivity?

A

Adverse/excessive pathological immune response

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7
Q

What is an immunogen?

A

Self-adjuvanting antigen (causes immune response on its own)

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8
Q

What is an immune complex?

A

Antibody-antigen complex

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9
Q

What is immunogenicity?

A

Ability of a substance to stimulate an immune response

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10
Q

What are DAMPs?

A

Damage Associated Molecular Patterns
- Molecules released by non-apoptotic cell death —> activates innate immune system

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11
Q

What are PAMPs?

A

Pathogen Associated Molecular Patterns
- Common molecular patterns in pathogens and microbes (not found in host cells) —> stimulates innate immune response

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12
Q

What are PPRs?

A

Pattern Recognition Receptors
- Receptors for DAMPs and PAMPs

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13
Q

What are the 2 causes of hypersensitivity?

A
  1. Foreign antigens —> allergies
  2. Self antigens —> autoimmune disease
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14
Q

What are the 2 consequences of hypersensitivity reactions?

A
  1. Inflammation —> pain
  2. Tissue damage (can be fatal)
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15
Q

How many classifications of hypersensitivity are there?

A

4
- Type I, II, III, IV

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16
Q

What do all hypersensitivity reactions require?

A

Adaptive immunological memory to antigen

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17
Q

Which type of immune response is involved in hypersensitivity?

A

Adaptive

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18
Q

What are the 5 antibody isotopes?

A
  1. IgG
  2. IgD
  3. IgE
  4. IgA
  5. IgM
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19
Q

What is the structure of IgG antibodies?

A

Normal
- V-L, V-H, C-L
- C-γ1, 2, 3
- Double bond

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20
Q

What is the structure of IgD antibodies?

A

Normal
- V-L, V-H, C-L
- C-δ1, 2, 3
- Single bond

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21
Q

What is the structure of IgE antibodies?

A

Normal
- V-L, V-H, C-L, C-γ2, C-γ3
- C-ε1, 2, 3, 4
- 2 bonds

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22
Q

What is the structure of IgA antibodies?

A

Dimer —> 2 connected by J chain
- V-L, V-H, C-L
- C-α1, 2, 3
- single bonds
(like 2 IgDs)

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23
Q

What is the structure of IgM antibodies?

A

Pentamer —> 1 J chain + 4 disulfide bridges
- V-L, V-H, C-L
- C-μ1, 2, 3, 4
(like 5 IgEs)

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24
Q

What is the function of IgG3?

A

Activate phagocytosis
- Complement and FcR mediated phagocytosis

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25
What is the function of IgE?
Stimulate mast cell degranulation
26
What is special about IgA?
Can cross mucosal epithelium
27
What is clonal expansion of T cells?
Rapid proliferation when naive T cell encounters antigen
28
What does clonal expansion of T cells result in? (2)
1. Effector T cells 2. Memory T cells
29
What is the main function of Treg cells?
Immune tolerance
30
What is the main function of Th17 cells?
Extracellular bacteria and fungi immune response
31
What is the main function of Th2 cells?
Allergic and anti-helminth response
32
What is the main function of Tfh cells?
B cell help in germination centres
33
What is the main function of Th1 cells?
Control intracellular pathogen response
34
What is type 1 hypersensitivity?
Allergic reaction (immediate/anaphylactic hypersensitivity)
35
What type of hypersensitivity are allergic reactions?
Type I
36
What are 4 examples of diseases caused by type 1 hypersensitivity?
1. Asthma 2. Allergic rhinitis 3. Urticaria 4. Atopic dermatitis
37
What are the general rules for deciding hypersensitivity type occurring?
1. Type I ---> allergic reaction 2. Type II ---> antibody issues 3. Type III ---> response not cleared (autoimmunity) 4. Type IV ---> delayed inflammation
38
Which antibodies mediate type 1 hypersensitivity?
IgE
39
Why do people have allergies?
Produce IgE antibodies against common multivalent antigens - IgE rarely found in circulation of non-allergic people
40
What are the 5 common types of allergen?
1. Foods 2. Plants 3. Animal dander 4. Drugs 5. Insect products
41
How are allergies diagnosed?
Skin prick test ---> see if stimulates inflammation
42
Which 2 Th cells are stimulated by IgE in type 1 hypersensitivity?
1. Th2 cells 2. Tfh cells
43
Which 2 cytokines are involved in type 1 hypersensitivity?
1. IL-4 2. IL-13
44
What are the effects of IL-4 and IL-13 in type 1 hypersensitivity?
Promote B cell switch to antigen-specific IgE production
45
Which cells do IgE antibodies bind to and why?
1. Mast cells 2. Basophils - High infinity IgE receptors (FcεRI)
46
What happens when cell bound IgE encounters an allergen?
Crosslinking ---> degranulation
47
What are the 6 steps of type 1 hypersensitivity?
1. IgE encounters cognate antigen 2. IgE activates Th2 and Tfh cells 3. IL-4 and IL-13 released 4. Stimulates B cell switch to antigen-specific IgE ---> lots of antibodies 5. IgE bind to mast cells and basophils 6. Cell-bound IgEs stimulate degranulation ---> antimicrobial chemicals released
48
What are the 10 mediator molecules of type 1 hypersensitivity?
1. Histamine 2. Serotonin 3. ECF-A (eosinophil) 4. NCF-A (neutrophil) 5. Proteases 6. Platelet-activating factor 7. Leukotrienes 8. Prostaglandins 9. Bradykinin 10. Cytokines
49
Which 2 molecules lead to an allergic reaction in type 1 hypersensitivity?
1. Histamine 2. Cytokines
50
What are the 3 phases of a type 1 hypersensitivity reaction and which cells are involved?
1. Early phase ---> mast cells 2. Later response ---> neutrophils 3. Late response ---> eosinophils and Th2 cells
51
When do the early, later and late responses occur in type 1 hypersensitivity?
1. Early ---> minutes 2. Later ---> hours 3. Late ---> 3-4 days
52
What is type II hypersensitivity known as?
Antibody-mediated cytotoxic hypersensitivity
53
Which 2 antibodies are involved in type II hypersensitivity and what do they do?
1. IgG 2. IgM
54
What are 4 examples of a cause of type II hypersensitivity?
1. Mismatched blood transfusion 2. Haemolytic disease of newborns 3. Immune thrombocytopenia 4. Graves disease
55
How can blood transfusions cause type II hypersensitivity?
Wrong type ---> wrong antibodies
56
How can haemolytic diseases of newborns cause type II hypersensitivity?
HTRs and HDFN
57
Why can immune thrombocytopenia cause type II hypersensitivity?
Antibodies produced again platelet surface proteins
58
Why can Graves disease cause type II hypersensitivity?
Thyroid stimulating antibodies ---> bind to thyrotropin receptor ---> over secretion of thyroid hormones
59
Can type II hypersensitivity be caused by foreign and self antigens?
Yes
60
What are the 3 mechanisms of type II hypersensitivity diseases?
1. Anti-receptor activity 2. ADCC 3. Classical complement cascade
61
What is ADCC?
Antibody Dependant Cell-mediated Cytotoxicity - Bind to FcRs (constant region of IgGs and IgMs) of granulocytes and NK cells
62
What happens if ADCC antibody-antigen complexes form resulting in type II hypersensitivity? (2)
1. Lysis of target cells 2. Release of inflammatory mediators (cytokines and chemokines)
63
Which cells are involved in type II hypersensitivity reactions?
1. Granulocytes 2. NK cells
64
What are the 3 consequences of type II hypersensitivity reactions?
Tissue injury: 1. Inflammation (local or systemic) Cell depletion: 2. Loss of function of tissue 3. Organ function imbalance
65
What are the 3 steps of type II hypersensitvity?
1. IgG or IgM antibodies bind to antigen 2. Anti-receptor activity/ ADCC/ classical complement 3. Lysis of target cells and inflammation
66
What is type III hypersensitivity known as?
Immune complexe driven disease
67
When do type III hypersensitivity reactions occur?
Immune complexes not cleared eg. self-antigens
68
Which complexes cause type III hypersensitivity?
Immune complexes
69
What is an example of type III hypersensitivity?
Autoimmunity
70
What are the 6 symptoms of type III hypersensitivity?
1. Fevers 2. Rashes 3. Joint pain 4. Proteinuria - vasculitis, glomerulonephritis, arthristis
71
What are 3 examples of diseases caused by type III hypersensitivity?
1. SLE ---> antibodies against nuclear DNA/proteins 2. MS 3. Rheumatoid arthritis
72
What are 3 examples of foreign antigens causing type III hypersensitivity?
1. Persistant hepatitis virus 2. Drugs 3. Serum sickness
73
What is serum sickness?
Type III hypersensitivity from injection or administration of foreign proteins or antigens
74
Which antibodies are involved in type III hypersensitivity?
IgG
75
Which types of hypersensitivity result in inflammation?
All - Type I, II, III ---> immediate
76
What is type IV hypersensitivity also known as? (2)
1. Delayed-type hypersensitivity 2. T cell mediated hypersensitivity
77
What is different about type IV hypersensitivity and why?
Delayed inflammation - Requires DCs ---> APCs ---> Naive T ---> Memory T - Time taken to generate antigen specific memory T cells
78
When is peak immune response seen in type IV hypersensitivity?
2-3 days after inflammation
78
How long do type IV hypersensitivity reactions take to occur and why?
Several weeks
79
What are the 4 steps of type IV hypersensitivity reaction?
1. Dendritic cell recognises foreign antigen ---> APC 2. Antigen presented to naive T cell ---> activated 3. T cell recruitment and expansion 4. Antigen-specific memory T cells produced ---> response
80
What is are 7 examples of type IV hypersensitivity?
Th1 beased: 1. Poison ivy 2. Nickel salts 3. Hair dyes 4. Tuberclin test Th2: 5. Asthma 6. Allergens CTLs: 7. Graft rejection
81
How does poison ivy stimulate type IV hypersensitivity?
- Urishol acts as hapten ---> binds to skin proteins ---> antigen ---> Th1 response - Re-exposure ---> memory T produce IFNγ ---> pro-inflammatory macrophage activation ---> blister-like lesions
82
Which cells drive inflammation in type IV hypersensitivity?
T cells
83
What is an example of 2 pathogens causing type IV hypersensitivity?
1. Measles 2. M. tuberculosis
84
Which type of hypersensitivity is involved in the tuberculin skin test?
Type IV
85
How many hypersensitivity types can be involved in the cause of 1 disease?
Multiple
86
What are the immune mediators of each type hypersensitivity?
1. IgE 2. IgG/M 3. Immune complexes 4. T cells
87
What is the general mechanism of type I hypersensitivity?
Cell-bound IgE activates mast cell and basophil degranulation
88
What is the general mechanism of type II hypersensitivity?
Antibodies against cell surface antigens destroy cells via ADCC or classical complement
89
What is the general mechanism of type IV hypersensitivity?
Sensitised T cells activate macrophages via cytokines
89
What is the general mechanism of type III hypersensitivity?
Antigen-antibody complexes cause neutrophil activation via complement

1.3 POM Immunology (13 decks)

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