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Year 1 HLB Respiratory > Allergy and Hypersensitivity > Flashcards

Allergy and Hypersensitivity Flashcards

1
Q

What is an allergy?

A
  • response from immune system
  • immune response damages the body
  • can be non pathogenic (dust, food)
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2
Q

What is hypersensitivity?

A
  • inappropriate activation of immune response
  • response is due to none pathogenic antigens
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3
Q

What are the 2 most common immune responses that occur in the body that are triggered by an allergy?

A
  • ⬆️ vascular permeability (vascular stage)
  • inflammation (damages tissue, unnecessarily) which are neutrophili followed by macrophage stage
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4
Q

What are local allergic reactions?

A
  • antigen interacts with a specific body site
  • allergic response is confined to specific site or tissue
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5
Q

What are a few examples of a local allergic reaction?

A
  • asthma (lungs)
  • food allergy (GI tract)
  • atopic dermatitis (skin)
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6
Q

What does anaphylaxis mean?

A
  • system wide response
  • antigen causing allergy needs to be systemic circulated
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7
Q

Why could an intravenous injection like penicillin cause a systemic response as seen in anaphylaxis instead of a local response?

A
  • if allergic to penicilin
  • intravenous means it can enter anywhere in the body
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8
Q

What is anaphylactic shock?

A
  • dangerous system wide response to antigen
  • can be fatal
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9
Q

Is hypersensitivity specific to the innate or adaptive immune system?

A
  • it can affect both
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10
Q

What are allergans?

A
  • antigens that initiate an allergic reaction
  • allergic reactions are immune responses
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11
Q

How many classifications of hypersensitivity are there?

A
  • 4
  • types I, II, III and IV
  • always written as roman numerals
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12
Q

What antibody is involved in type I hypersensitivity?

A
  • IgE
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13
Q

How quickly do type I hypersensitivity reactions take to occur?

A
  • almost immediately
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14
Q

Which classification of hypersensitivity are most allergic reactions?

A
  • type I
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15
Q

What other names is type I hypersensitivity called?

A
  • antibody mediated
  • immediate
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16
Q

Which part of the IgE antibody binds with the antigen?

A
  • variable region
  • also known as the Fab (fragment antigen binding)
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17
Q

Which part of the IgE antibody binds with the cells of the immune system?

A
  • Fc region
  • referred to as the constant region
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18
Q

Which cells of the immune system does the Fc portion of the antibody bind to in allergic reactions?

A
  • mast cells
  • basophils
  • eosinophils
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19
Q

What is the FcεRI, commonly referred to as the epsilon Fc receptor?

A
  • specific Fc receptor located on
  • mast cells, basophils and eosinophils
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20
Q

What type of transmembrane receptors are Fc receptors on cell surface?

A
  • receptor tyrosine kinase
  • enzyme induced receptors
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21
Q

Once bound to the Fc receptors of mast cells, basophils and eosinophils, what do the receptor tyrosine kinase do intracelluarly?

A
  • cause signalling cascade
  • facilitated by phosphorylation
  • kinase phosphorylates
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22
Q

What is the purpose of the signalling cascade inside mast cells, basophils and eosinophils once the Fc portion of the antibody has bound to the Fc receptors?

A
  • degranulation
  • release of inflammatory mediators
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23
Q

Is the release of IgE antibodies only released during type I hypersensitivity?

A
  • no
  • IgE is important for parasitic infections
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24
Q

What classification of hypersensitivity are all allergies?

A
  • type I
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25
Q

What are epitopes?

A
  • part of antigen that binds to antibody
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26
Q

Do antigens have just one epitope?

A
  • no
  • pollen has lot of epitopes
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27
Q

When exposed to an allergen (antigen causing allergic reaction) for the first time what happens to the B cells of the adaptive immune response?

A
  • become sensitised to antigen
  • B cells present antigen on cell surface via MHC-II
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28
Q

When exposed to an allergen (antigen causing allergic reaction) for the first time. How do T helper cells bind to the antigen presenting cell as part of the adaptive immune system?

A
  • T helper cells receptors bind to MHC-II
  • CD4 check MHC-II
  • CD40L (ligand) binds to CD40 on B cell to check cell
  • 3 checks in total
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29
Q

When exposed to an allergen (antigen causing allergic reaction) for the first time, and after being activated by T helper cells, what do B cells then do as part of the adaptive immune response?

A
  • differentiate into plasma and memory cells
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30
Q

When exposed to an allergen (antigen causing allergic reaction) for the first time, and after differentiating into memory and plasma cells, what do B plasma cells do?

A
  • secrete antibodies
  • antibodies bind to mast cells, basophils and eosinophils
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31
Q

Do you automatically have an allergic reaction when exposed to an allergen the first time?

A
  • no as it takes 1-2 weeks to occur
  • 2nd time exposed it will be fast acting
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32
Q

What are some common examples that can cause type I hypersensitivity?

A
  • pollens (rye grass, ragweed, timothy and birch trees)
  • foods (nuts, eggs, seafood, peas, beans and milk)
  • drugs (penicillin, sulphonamides, anaesthetics)
  • insects (bee, cockroaches, ants, dust mites)
  • miscellaneous (mold, animal hair, latex, vaccines, serum)
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33
Q

What are some common examples of type I hypersensitivity?

A
  • asthma
  • hay fever
  • hives
  • food allergies
  • eczema
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34
Q

Asthma is an example of type I hypersensitivity, what is released by mast cells during degranulation that causes asthma?

A
  • histamine
  • initiates an immune response
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35
Q

Where is histamine located?

A
  • inside granules of mast cells
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36
Q

What does histamine bind with?

A
  • histamine receptor or H1 receptor
37
Q

Where are histamine or H1 receptors located in the lungs?

A
  • smooth muscle on tunica media
38
Q

Once histamine has been released and bound to the H1 receptors on smooth muscle, what happens in asthma?

A
  • vascular permeability ⬆️
  • mucus production ⬆️
  • smooth muscle vasoconstriction ⬆️
39
Q

In addition to histamine, what 2 other molecules are released that are 1000 fold more active than histamines?

A
  • leukotrienes
  • prostoglandins
40
Q

What type of cell surface receptor are histamine or H1 receptors?

A
  • GPCR - specifically Gaq - ⬆️ Ca2+ released causing bronchoconstriction
41
Q

How many stages are there in asthma?

A
  • 2
42
Q

What are the 2 stages in asthma?

A
  • early response - late phase reaction
43
Q

During early response in asthma, how is this treated effectively?

A
  • inhalers
44
Q

In the late phase response, in order for immune cells to bind onto the endotheial cells in blood vessels what is increased on the surface of endothelial cells?

A
  • adhesion molecules
  • ⬆️ binding of immune cells
45
Q

What is the hygiene hypothesis?

A
  • no exposure to non harmful antigens when younger - ⬆️ risk of body identifying harmless allergens as dangerous
46
Q

What is type II hypersensitivity?

A
  • antibodies bind to cells containing antigen
  • these are host cells that appear infected
  • cells are lysed even though they are not infected
47
Q

Which antibodies are involved in type II hypersensitivity?

A
  • generally IgG
  • sometimes IgM
48
Q

Once bound the antigen-antibody complex has been formed on host tissue, what are the 3 ways these host cells are killed?

A

1 - compliment system (C3B)

2 - antibody-dependent cell-mediated cytotoxicity (ADCC)

3 - opsonisation

49
Q

What is the antibody-dependent cell-mediated cytotoxicity (ADCC) involved in type II hypersensitivity?

A
  • antibodies (IgG and IgM) bind to antigens
  • natural killer cells (NKC) bind to antibodies on cells
  • NKC lyse cells using toxic granules
50
Q

Transfusion reactions are an example of II hypersensitivity, what can happen if the wrong blood is transfused?

A
  • blood contains specific antigens A, B or H
  • determines our blood type
  • if blood with wrong antigen is present the body will attack and kill red blood cells as they do not have self antigens (correct A, B or H antigen)
51
Q

What is intravascular haemolysis?

A
  • rupture of red blood cells - can happen if wrong blood is transfused
52
Q

What are Rhesus antigens as an example of type II hypersensitivity?

A
  • antigens on blood
  • if mother is Rh- and father is Rh+ this is bad
  • mothers IgG cross placenta and destroy fetal blood cells
  • only occurs in second baby though
53
Q

How does Malaria trigger type II hypersensitivity?

A
  • antigen from P. falciparum parasite binds to blood
  • antibodies trigger haemolysis (rupture of red blood cells)
54
Q

What is drug induced haemolytic anaemia as an example of type II hypersensitivity?

A
  • drug bind to proteins in the blood
  • drug recognised as foreign antigen and antibodies bind
  • immune cells attack the drug
  • penicillin is an example
55
Q

What is type III hypersensitivity?

A
  • extensive immune complexes form
  • immune complexes cannot be cleared and aggregate
  • generally IgM antibodies, that then switch to IgG antibodies
56
Q

What are immune complexes?

A
  • multiple antibodies bind with multiple epitopes on antigens
  • forms aggregates of antibody-antigen complexes
  • insoluble so get stuck to blood vessels
57
Q

What are the 2 most common causes why immune complexes cannot be cleared?

A

1 - disorder of phagocytic machinery

2 - phagocytes cannot access antigens to phagocytise

58
Q

If immune complexes are not cleared what will they create at the site where they are present?

A
  • create aggregates
  • induce granulation from mast cells
  • inflammation follows
  • complement system activated
59
Q

Do the immune complexes form from soluble antibodies or those bound to host cells?

A
  • soluble antibodies
60
Q

Where do immune complexes get deposited in tissue?

A
  • move around in circulation - become deposited in capillary beds
61
Q

If immune complexes become deposited in capillary beds, what can this cause to the capillary beds?

A
  • inflammation - vasculitis
62
Q

What are the 2 most common chronic problems immune complex deposition can cause in the body?

A

1 - arthritis 2 - glomerulonephritis (inflammation of kidneys)

63
Q

What is arthus reaction when caused by an insect bite?

A
  • type III hypersensitivity
  • immune complexes form with antigen
64
Q

What are some common autoimmune disease examples of type III hypersensitivity?

A

1 - rheumatoid arthritis 2 - multiple sclerosis 3 - systemic lupus erythematosus

65
Q

What are some common infection disease examples of type III hypersensitivity?

A

1 - meningitis 2 - hepatitis 3 - mononucleosis 4 - malaria 5 - trypanosomiasis 6 - poststreptococcal glomerulonephritis

66
Q

What are some common drug reactions as examples of type III hypersensitivity?

A

1 - penicillin 2 - sulphonamides

67
Q

What are some common arthus reactions as examples of type III hypersensitivity?

A

1 - farmers lung (actinomycetes (bacteria) in hay) 2 - pigeon fanciers disease (faeces)

68
Q

What is type IV hypersensitivity?

A
  • a cell mediated response to antigens
69
Q

In type IV hypersensitivity are antibodies involves?

A
  • no
  • only hypersensitivity classification with no antibodies
70
Q

What cells are involved in type IV hypersensitivity?

A
  • antigen presenting cells (macrophages+Langerhans)
  • T helper cells
71
Q

What are the 2 stages of type IV hypersensitivity?

A

1 - sensitisation

2 - effector phase

72
Q

What is the sensitisation phase of type IV hypersensitivity?

A
  • antigen presenting cells present antigen
  • T helper cells bind to MHC-II complex
  • T helper cells are activated by cytokines
73
Q

Once T helper cells are activated in type IV hypersensitivity, what do they differentiate into?

A
  • T helper effector cells - T helper memory cells
74
Q

How long does sensitisation in type IV hypersensitivity generally take?

A
  • 1-2 weeks similar to normal immune response
75
Q

What is type IV hypersensitivity also referred to as?

A
  • delayed type hypersensitivity
76
Q

Once sensitised to the antigen how long, how long does the effector phase of type IV hypersensitivity take to initiate?

A
  • 24-48 hours
77
Q

Once sensitised, what do T helper cells do in the effector phase of type IV hypersensitivity?

A
  • produce cytokines
  • cytokines activate macrophages and immune cells
  • macrophages are responsible for most tissue damage
78
Q

In type IV hypersensitivity is the inflammatory response local or regional?

A
  • generally local - like poison ivy on specific skin that touched it
79
Q

What are a few intracellular bacteria that can cause type IV hypersensitivity?

A

1 - mycobacterium tuberculosis

2 - mycobacterium leprae

3 - brucella abortus

4 - listeria monocytogenes

80
Q

What are a few intracellular viruses that can cause type IV hypersensitivity?

A

1 - herpes simplex virus

2 - variola (smallpox)

3 - measles

81
Q

What are a few intracellular fungi that can cause type IV hypersensitivity?

A

1 - pneumocystis carinii 2 - candida albicans 3 - histoplasma capsulatum 4 - cryptococcus neoformans

82
Q

What is an intracellular parasite that can cause type IV hypersensitivity?

A
  • leishmania sepsis
83
Q

What are a few contact antigens that can cause type IV hypersensitivity?

A

1 - hair dyes 2 - nickel salts 3 - poison ivy 4 - poison oak 5 - picryl chloride

84
Q

What are 2 of the most common causes of a type IV hypersensitivity?

A
  • graft rejection
  • contact dermatitis
85
Q

Which classification is most commonly associated with a cough?

A
  • type 1 hypersensitivity
86
Q

Although coughs are generally not serious there are some occasions when they may be a red flag for a serious pathology. What duration of a cough with a wheeze would be classed as a red flag?

A
  • >3 weeks
87
Q

Although coughs are generally not serious there are some occasions when they may be a red flag for a serious pathology. What may recurrent chest infections be a sign of and a red flag?

A
  • inflammation of the pleural of lungs and thoracic cavity - chest pain is also common
88
Q

Although coughs are generally not serious there are some occasions when they may be a red flag for a serious pathology. Dyspnoea is laboured breathing, when can this be classed as serious and classed as a red flag?

A
  • when the patient coughs up phlegm every morning - >3 months
89
Q

Although coughs are generally not serious there are some occasions when they may be a red flag for a serious pathology. Why is a persistent nocturnal cough a red flag?

A
  • could be underlining pathology - infection - cancer - lung disease

Year 1 HLB Respiratory (25 decks)

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