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Type I hypersensitivity Flashcards

1
Q

Inhaled materials

A
  • plant pollens
  • dander of domesticated animals
  • mold spores
  • feces of very small animals - house dust mites
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2
Q

injected materials

A
  • insect venoms
  • vaccines
  • drugs
  • theraputic proteins
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3
Q

ingested matierals

A
  • food
  • orally administered drugs
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4
Q

contacted materials

A
  • plant leaves
  • industrial products made from plants
  • synthetic chemicals in industrial products
  • metals
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5
Q

Type I hypersensitivity locations

A
  • skin
  • resperatory tract
  • gut
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6
Q

The four types of hyper sensitivity reactions are characterized by

A

the molecules and cell types involved

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7
Q

Antibody induced reactions

A

Type I-III

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8
Q

T cell induced reaction

A

Type IV

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9
Q

Type I main antibody

A

IgE

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10
Q

Type II and III main antibody

A

IgG

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11
Q

Type IV main cells

A

T cells and macrophages

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12
Q

Type I has a broad variety of severity

A

can be anything from seasonal allergies to life threatening anaphylaxis

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13
Q

Type I - IgE mediated Hypersensitivity

A

Results from antigen binding to antigen specific IgE which is bound to its FcR on mast cells.

Mast cells degranulate and release inflammatory mediators and histamine
- can be from runny nose to death by asphyxiation
- known as immediate hypersensitivity
- commonly caused by inhaled particulate antigens such as pollen

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14
Q

Type I hypersensitivity:

A

the mast cell is at the heart of the response

  • IgE is already bound on the mast cell surface htorugh Fc receptor (epsilon).
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15
Q

allergic reactions develop

A

AFTER an individual is exposed and sensitized.

NOBODY is born allergic.

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16
Q

First exposure to pollen (example of an allergy)

A

mechanism induces Th2 type T helper response, producing IL4, stimualting B cell isotype switching to IgE (plasma cells), and then the IgE binds to surface of mast cells, which then can granulate upon a secondary encounter with the allergen.

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17
Q

systemic anaphylaxis

A
  • drugs
  • serum
  • venoms
  • peanuts

Respnse: systemic
- Edema
- Increased vascular permeability - causes vessels to become more permeable and low blood pressure - heart has to work harder to pump blood. and oxygen in tissue is way too low
- Tracheal occlusion
- circulatory response
- death

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18
Q

wheal and flare

A

skin localized
- insect bites
- allergy testing

Swelling and redness of skin

Response: local increase in blood flow and vascular permeablity

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19
Q

allergic rhinitis (hay fever)

A

Pollens, dust mite feces

Response: local, edema of nasal mucosa and irritation of nasal mucosa.

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20
Q

Bronchial asthma

A

Pollens, dust mite

Reponse: local
- bronchial constriction
- increased mucus production
- airway inflammation

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21
Q

Food allergy

A

shellfish
milk
eggs
fish
wheat

Response: systemic
- vomiting
- diarrhea
- pruritis (itching)
- Urticaria (hives)
- anaphylaxis

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22
Q

Allergic rhinitis case study

A
  • among most common chronic dieases
  • sneezing, drainage, nasal stuffiness
  • 2004 study estimates that 25.3 million Americans, 6.7<18 years old
  • seasonal or perennial (spring/summer/fall)
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23
Q

trees

A

highest in early spring

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24
Q

grass

A

highest in late spring

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25
weeds
summer - fall
26
skin testing (diagnostic)
- must be off all antihistamines - percutaneous
27
Serum specific IgE testing
- used when skin testing cannot be performed
28
wheal
swelling
29
flare
red color
30
allergic responses have..
early and late phase
31
early phase of an allergic response
Wheal (swelling) and flare (redness from spreading wheal) - due to immediate mast cell degranulation
32
late phase of an allergic response
Generalized swelling spreading out from initial site of exposure - due to **leukotrienes, cytokines, and chemokines** produced by mast cells after initial degranulation.
33
asthmatic reaction also have..
early and late phase - resulting in decreased breathing capacity Breathing capacity drops very fast initially, then goes back to normal
34
which of the following rxn's requires mast cells to synthesize new immunomodulatory proteins?
Late phase
35
Inflammatory mediators produced by mast cells **Present in PreFormed granules**
- Tryptase, chymase, cathepsin G, carboxypeptidase - **histamine, heparin** - TFN-alpha
36
biological effects of histamine and heparin
- Toxic to parasites - Increase vascular permeability - cause smooth muscle contraction
37
TNF-alphs promotes
inflammation, stimulates cytokine production by many cell types, activates endothelium
38
Enzymes: Tryptase, chymase, catepsin G, carboxypeptidase
remodeling of connective tissue matrix
39
Inflammatory mediators produced by mast cells Produced in response to mast cell activation
- IL4, IL13 - IL3, IL5, GM-CSF - CCL3 - Leukotrinenes - PLT activating factor
40
IL4 and IL13
stimulate and amplify Th2 cell response
41
IL3, IL5, GM-CSF
promote eosinophil production and activation
42
CCL3 (chemokine)
chemotactic for monocytes, macrophages and neutrophils
43
Leukotrienes
- Cause smooth muscle contraction - Increase vascular permeability - Cause mucus secretion
44
PLT activating factor
- Chemotactic for leukocytes - Amplifies production of lipid mediators - Activates neutrophils, eosinophils, platelets
45
How do we treat allergic rhinitis?
- Avoidance - antihistamines - nasal steroids - immunotherapy 1. Give increasing concentration of allergens to induce tolerance 2. **IgE** = initial increase in specific IgE levels but long term decrease in specific IgE 3. **IgG** = allergen specific IgG1, IgG4, IgA increase with immunotherapy 4. other lymphocyte markers - IL10,TGFbeta prod. from (CD4+, CD25+ Tregg cells) 5. ***Shift in Th1/Th2 balance*** (want to favor Th1)
46
Effects of IgE mediated allergic reactions vary with the site of mast cell activation
- Gastrointestinal tract - Airways - Blood vessel
47
GI tract (mast cell activation and granule release)
Increase fluid secretion, increased peristalsis - expulsion of GI tract contents: diarrhea and vomitting
48
Airways (mast cell activation and granule release)
Decreased diameter, increased mucus secretion - expulsion of airway contents (phlegm, coughing)
49
blood vessel (mast cell activation and granule release)
Increased blood flow, increased permeability - edema - inflammation - increased lymph flow and carriage of antigen to lymph nodes
50
Systemic anaphylaxis secondary to food ingestion symptoms:
Cardiovascular (most threatening) - hypotension, tachyardia, bradycardia, shock, MI Respiratory - laryngeal/pharyngeal edema, rhinitis, wheezing, cough, shortness of breath Cutaneous - pruruitis, urticaria, angioedema, flushing GI - nausea, vomiting, diarrhea, abdominal cramping Ocular (least threatening) - pruritis, tearing, redness
51
How does epinephrine work against a systematic anaphylaxis reaction
1. contricts **blood vessels** - decreases swelling and increase BP 2. Increases **contraction and heart rate** 3. relaxes muscles around **airways in the lungs** 4. prevents release of additional allergic chemicals
52
food allergy
incidence of food allergy in the US ranges from 4-6% in children, 1-3% in adults Incidence is rising, especially peanuts allergies (doubled last few years)
53
major allergenic foods in children
milk, egg, soy, wheat, peanut, tree nut
54
major allergenic foods in adults
peanut, tree nut, shellfish
55
<0.35 kU/L
indicates a negative test
56
Allergies may be lifelong
peanut tend to be lifelong, although studies show that abt 20% of children with peanut allergt do **eventually outgrow their allergy** Children that are **allergic** to milk, egg or soy, were most likely to **outgrow their allergies** The likelihood of **outgrowing shellfish, tree nut, and peanut allergies was significantly lower**.
57
systematic anaphylaxis :
caused by allergens that reach the bloodstream and activate mast cells systematically
58
Heart and vascular system (anaphylaxis)
- increased capilarry permability and entre of fluid into tissues - swelling of tissues - including tongue - loss of BP - Reduced oxygen to tissues - irregylar heartbeat - anaphylactic shock - loss of conciousness
59
Respiratory tract (anaphylaxis)
- contraction of smooth muscle and constriction of throat and airways - difficulty breathing and swallowing - wheezing
60
GI (anaphylaxis)
1. contraction of smooth muscle 2. stomach cramps 3. vomiting 4. fluid outlflow into gut 5. diarrhea
61
prevention
minimize exposure - remove allergen from diet or environment
62
pharmalogical treatment
minimize impact of exposure - antihistamines - corticosteroids - epinephrine
63
desensitization treatment
- give allergy in controlled escalating doses in an attempt to shift antibody isotype from IgE to IgG4 - or induce anergy in T cells using MHC peptide complexes
64
if you coulld engineer a T cell response to inhibit tyep I hypersensitivity, which type of Th susbset would you enlist?
Th1, Treg

Immunology (18 decks)

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