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Immunology > Exam 3: Hypersensitivity Type I > Flashcards

Exam 3: Hypersensitivity Type I Flashcards

(61 cards)

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1
Q

what type of immune response is hypersensitivity type I

A

antibody mediated immune response

humoral

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2
Q

what kind of antigens trigger type I hypersensitivity

A

allergies

parasite worms

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3
Q

characteristics of type I hypersensitivity (4)

A

exaggerated Th2 response

excessive amounts of IgE = atopy

genes + environmental factors = allergies

intestinal microflora

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4
Q

what does early contact with allergens lead to

A

less susceptible to get allergies

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5
Q

what are some non microbial antigens that can cause allergies

A

food

insects

pollen

fur

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6
Q

what is the normal concentration of IgE in serum

A

low

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7
Q

what happens to IgE concentration in type I hypersensitivity

A

IgE overproduction

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8
Q

what happens to IL-4 in type I hypersensitivity

A

IL-4 overproduction

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9
Q

what does IL-4 overproduction cause

A

increased Th2 activation and B cell stimulation

when B cells differentiate –> IL-4 increases production of IgE

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10
Q

what are the receptors of IgE and what type of binding to the antibody do they have

A

irreversible binding to antibody

FcεR
FcεRI
FcεRII

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11
Q

FcεR
FcεRI
FcεRII

A

FcεR - has high affinity and irreversible binding

FcεRI - present in mast cells, basophils, neutrophils, eosinophils, macrophages, dendritic cells

FcεRII - present in B cells, NK cells, macrophages, dendritic cells, eosinophils, platelets

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12
Q

mechanism of type I hypersensitivity reactions

A

numerous biologically active molecules are released by mast cells and basophils when antigen cross-links two IgE molecules on the mast cell surface

some are produced immediately, others may be synthesized within minutes or hours

  1. antigen + mast cell with IgE
  2. Degranulation - cytokines, enzymes, chemotactic molecules, vasoactive molecules
  3. acute inflammation and systemic effects
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13
Q

the role of IL-4 in induction if IgE response - normal humoral response

A

IL-4 is produced by Th2 cells

Once released, IL-4 promotes development of more Th2 cells

Th2 cells are major sources of this cytokine and promote IgE responses

Degranulation of mast cells also releases IL-4 to further promote this reaction

NK cells may serve as an initial source of IL-4

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14
Q

what inhibits response of IL-4

A

Response to IL-4 inhibited by IFN-y and IL-12

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15
Q

the allergy loop

A

dendritic cells express trimeric FcεRI as can bind antigen-IgE complexes

this antigen, once processed, stimulates Th2 responses

these Th2 cells in turn secrete cytokines, which further promote the IgE response

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16
Q

mast cell resposne

A

the combination of Fcε receptors with their ligands stimulates many different responses in mast cells

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17
Q

what is CR2

A

CR2 is a complement receptor located in B cells, T cells, and dendritic cells

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18
Q

mast cell response FcεRI

A

antigen –> IgE –> FcεRI (high affinity) –> mast cell degranulation, eosinophil ADCC, dendritic cells, macrophages

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19
Q

mast cell response FcεRII

A

antigen –> IgE –> FcεRII (low affinity) –> B cell down regulation, Macrophage phagocytosis, NK cells, Dendritic cells, Eosinophils

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20
Q

mast cell response FcεRIII

A

CR2 –> FcεRIII –> B cell stimulation and survival

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21
Q

mast cell - characteristics

A

located in intestine, skin, airways, around nerves

close to blood vessels

release proinflammatory mediators

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22
Q

what do mast cells release in connective tissue/skin and what is their life span

A

histamine
heparin

life span > 6 months

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23
Q

what do mast cells release in intestine/lung and what is their life span

A

chondroitin sulfate
few histamine

life span < 40 days

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24
Q

mast cells - molecules released from exocytosed granules within seconds

A 
histamine
serotonin
tryptase
kallikreins
proteases
proteoglycans
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25
mast cells - eicosanoid synthesis and secretion within minutes
leukotrienes prostaglandins platelet activating factor These all induce inflammation
26
mast cells - cytokine synthesis and secretion over several hours
``` IL-4 IL-5 IL-6 IL-13 TNF-a MIP-1a ```
27
``` Biological properties of IL-33 Innate lymphocytes Macrophages Neutrophils B cells Th2 cells Eosinophils Basophils Mast cells Neurons ```
Innate lymphocytes - Th2 cytokines, IFN-y, TNF-a, IL-2 Macrophages - M2 polarization, tissue repair Neutrophils - phagocytosis B cells - IgM Th2 cells - IL-5, IL-13 --> exotoxins Eosinophils - IL-8, degranulation --> terminal effector cells of the allergic response Basophils - IL-3, IL-4, IL-6, IL-13, histamine, GM-CSF --> basophil differentiation in bone marrow Mast cells - IL-6, IL-13 --> degranulation in presence of IgE Neurons - itch
28
what does IL-33 do
stimulates the production of inflammatory cytokines and chemokines from many different cell types major mediator in type I hypersensitivity
29
what happens when an allergen binds to a IgE that is attached to a mast cell
the mast cell releases granules and begin to synthesize several other factors that have effects on GI tract, airways, blood vessels
30
effects of mast cell degranulation on GI tract
fluid secretion, peristalsis emptying of GI tract (diarrhea, vomiting)
31
effects of mast cell degranulation on respiratory tract
mucous secretion, bronchoconstriction difficulty breathing
32
effects of mast cell degranulation on blood vessels
increased vascular permeability movement of fluids, proteins, and cells out of blood vessels and into inflamed tissues
33
what inhibits mast cell degranulation
blocking a adrenoreceptors stimulating B adrenoreceptors: isoproterenol, epinephrine, salbutamol
34
what enhances mast dell degranulation
stimulation of a adrenoreceptors: norepinephrine, phenylephrine blocking B adrenoreceptors: propranolol
35
what happens when mast cell degranulation enhanced
immediate inflammation 10-20 minutes late phase reaction 6-12 hours
36
what happens when a receptor stimulated and B receptor blocked
Mast cells - enhanced degranulation Smooth muscle - contracts Blood vessels - constricts
37
what happens when B receptor stimulated and a receptor blocked
Mast cells - suppressed degranulation Smooth muscle - relaxes Blood vessels - dilates
38
what happens when basophils bind IgE
1. Bind IgE 2. Basophil degranulation 3. increasing vascular permeability
39
characteristics of basophils
long term allergic states (chronic allergic dermatitis) initiate helminth immune response as APC (Th2) protective role in helminth, tick, bacterial infections, degrade toxins in venom, contribute to tumor rejection
40
Eosinophils respond to
parasites pathogens PAMPs and DAMPs
41
eosinophils produce
oxidants and enzymes lipid mediators cationic granule proteins cytokines chemokines
42
eosinophils - oxidants and enzymes effects
tissue damage and inflammation
43
eosinophils - lipid mediators effects
pain smooth muscle contraction mucus production
44
eosinophils - cationic granule proteins effects
tissue damage and inflammation
45
eosinophils - cytokines effects
macrophage activation dendritic cell activation neutrophil activation endothelial cell activation
46
eosinophils - chemokines effects
T cell chemotaxis and activation
47
clinical type I hypersensitivity
allergic anaphylaxis milk allergy food allergy allergy to vaccines and drugs (penicillin) allergies to parasites, midges, black flies, stable flies, fleas allergic inhalant dermatitis atopic dermatitis (house dust mites, molds, trees, weeds, grass pollen) hygiene hypothesis
48
which breeds are more susceptible to atopic dermatitis
``` retrievers terriers beagles boxers bulldogs shar-pei ```
49
what is most affected in dogs with allergic anaphylaxis
liver - hepatic veins
50
what is affected in most species with allergic anaphylaxis
respiratory tract and intestines
51
what is used in severe allergic anaphylaxis reactions
epinephrine -- epi-pen
52
is allergic anaphylaxis a severe, life threatening systemic hypersensitivity reaction
yes | can be fatal
53
immune response in atopic dermatitis
``` allergens --> trauma --> keratinocytes --> cytokines --> TSLP --> sensory neurons (with input from IL-31) --> itch ```
54
which IL is most important in atopic dermatitis and what does it do
IL-31 Gives itching sensation
55
diagnosis of type I hypersensitivity
intradermal skin testing passive cutaneous anaphylaxis (PCA) measuring IgE
56
treatment of type I hypersensitivity
avoid exposure to allergen corticosteroids antihistamines B stimulants - epinephrine, isoprenaline, salbutamol a antagonists - methoxamine, phenyleprine allergen specific immunotherapy
57
intradermal allergy test
bunch of injections into skin to see which allergens you react to
58
immunotherapy
injections or oral drops injections or oral drops contain small amounts of the allergen --> vaccines objective of these vaccines is tolerance and increased IgG production (class switching from IgE)
59
why do we want increased IgG production in immunotherapy
higher amounts of IgG will compete with IgE to bind allergen and allergen will be eliminated/destroyed
60
canine atopic dermatitis
caninized anti-cIL-31 monoclonal antibody (mAb) mAb specifically targets and neutralizes canine IL-31 which is involved in sending itch signal to brain interrupts cycle of itch and inflammation how apoquel works
61
best treatment for type I hypersensitivity in humans
have a chihuahua dog because they help with asthma apparently but no scientific explanation (or evidence really)

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