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Immunology > Type I hypersensitivity > Flashcards

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
Q

weeds

A

summer - fall

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26
Q

skin testing (diagnostic)

A
  • must be off all antihistamines
  • percutaneous
27
Q

Serum specific IgE testing

A
  • used when skin testing cannot be performed
28
Q

wheal

A

swelling

29
Q

flare

A

red color

30
Q

allergic responses have..

A

early and late phase

31
Q

early phase of an allergic response

A

Wheal (swelling) and flare (redness from spreading wheal)
- due to immediate mast cell degranulation

32
Q

late phase of an allergic response

A

Generalized swelling spreading out from initial site of exposure
- due to leukotrienes, cytokines, and chemokines produced by mast cells after initial degranulation.

33
Q

asthmatic reaction also have..

A

early and late phase
- resulting in decreased breathing capacity

Breathing capacity drops very fast initially, then goes back to normal

34
Q

which of the following rxn’s requires mast cells to synthesize new immunomodulatory proteins?

A

Late phase

35
Q

Inflammatory mediators produced by mast cells

Present in PreFormed granules

A
  • Tryptase, chymase, cathepsin G, carboxypeptidase
  • histamine, heparin
  • TFN-alpha
36
Q

biological effects of histamine and heparin

A
  • Toxic to parasites
  • Increase vascular permeability
  • cause smooth muscle contraction
37
Q

TNF-alphs promotes

A

inflammation, stimulates cytokine production by many cell types, activates endothelium

38
Q

Enzymes: Tryptase, chymase, catepsin G, carboxypeptidase

A

remodeling of connective tissue matrix

39
Q

Inflammatory mediators produced by mast cells

Produced in response to mast cell activation

A
  • IL4, IL13
  • IL3, IL5, GM-CSF
  • CCL3
  • Leukotrinenes
  • PLT activating factor
40
Q

IL4 and IL13

A

stimulate and amplify Th2 cell response

41
Q

IL3, IL5, GM-CSF

A

promote eosinophil production and activation

42
Q

CCL3 (chemokine)

A

chemotactic for monocytes, macrophages and neutrophils

43
Q

Leukotrienes

A
  • Cause smooth muscle contraction
  • Increase vascular permeability
  • Cause mucus secretion
44
Q

PLT activating factor

A
  • Chemotactic for leukocytes
  • Amplifies production of lipid mediators
  • Activates neutrophils, eosinophils, platelets
45
Q

How do we treat allergic rhinitis?

A
  • 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
Q

Effects of IgE mediated allergic reactions vary with the site of mast cell activation

A
  • Gastrointestinal tract
  • Airways
  • Blood vessel
47
Q

GI tract (mast cell activation and granule release)

A

Increase fluid secretion, increased peristalsis
- expulsion of GI tract contents: diarrhea and vomitting

48
Q

Airways (mast cell activation and granule release)

A

Decreased diameter, increased mucus secretion
- expulsion of airway contents (phlegm, coughing)

49
Q

blood vessel (mast cell activation and granule release)

A

Increased blood flow, increased permeability
- edema
- inflammation
- increased lymph flow and carriage of antigen to lymph nodes

50
Q

Systemic anaphylaxis secondary to food ingestion

symptoms:

A

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
Q

How does epinephrine work against a systematic anaphylaxis reaction

A
  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
Q

food allergy

A

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
Q

major allergenic foods in children

A

milk, egg, soy, wheat, peanut, tree nut

54
Q

major allergenic foods in adults

A

peanut, tree nut, shellfish

55
Q

<0.35 kU/L

A

indicates a negative test

56
Q

Allergies may be lifelong

A

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
Q

systematic anaphylaxis :

A

caused by allergens that reach the bloodstream and activate mast cells systematically

58
Q

Heart and vascular system
(anaphylaxis)

A
  • 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
Q

Respiratory tract
(anaphylaxis)

A
  • contraction of smooth muscle and constriction of throat and airways
  • difficulty breathing and swallowing
  • wheezing
60
Q

GI (anaphylaxis)

A
  1. contraction of smooth muscle
  2. stomach cramps
  3. vomiting
  4. fluid outlflow into gut
  5. diarrhea
61
Q

prevention

A

minimize exposure
- remove allergen from diet or environment

62
Q

pharmalogical treatment

A

minimize impact of exposure
- antihistamines
- corticosteroids
- epinephrine

63
Q

desensitization treatment

A
  • 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
Q

if you coulld engineer a T cell response to inhibit tyep I hypersensitivity, which type of Th susbset would you enlist?

A

Th1, Treg

Immunology (18 decks)

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