Hypersensitivity Type I

Question 1

type I hyper. is mediated by?

Answer 1

IgE mediated opsonization
(Anaphylactic and Atopic)

Question 2

Type II Hyper. is mediated by?

Answer 2

IgM/IgG - mediated Opsonization
(Abs mediated)

Question 3

Type III hyper. is mediated by?

Answer 3

Immune complex

Question 4

Type IV HYper. is mediated by?

Answer 4

T-cells

Question 5

Which hypersensitivity type is not Abs Mediated?

Answer 5

Type IV

* type I, II, III are all abs mediated

Question 6

What triggers Type I hyper.

Answer 6

1) Systemic Anaphylaxis (e.g. penicillin, seafood, drugs or bee sting allergies)
2) Localized Hypersensitivity rxn (e.g. Allergic rhinitis (hay fever), asthma, atopic dermatitis (eczema), food allergies)

*Anaphylactic and Atopic

Question 7

Treatment for Type I hypersensitivity caused by Systemic anaphylaxis (e.g. seafood, bee sting allergy)?

Answer 7

Epinephrine
(rapidly reverses the action of histamine on smooth muscle contraction and capillary dilation)

Question 8

What triggers Type II hyper.

Answer 8

Abs bind to cell-surface antigens –> cellular destruction, inflammation, and cellular dyfunction

Question 9

Examples of type II hypersensitivity

Answer 9

1. Transfusion reactions
2. Hemolytic disease of the newborn
3. Drug-induced hemolytic anemia

Question 10

The 2 phases of Type 1 Hyper.

Answer 10

1)Immediate - minutes
2)Delayed -hours

Question 11

Explain the Immediate phase of type 1 hyper. upon contact with allergen

Answer 11

Immediate (min) : Antigen crosslinks preformed IgE on presensitized mast cells –> immediate degranulation –> release of histamins (vasoactive amine), Tryptase (marker of mast cell activation), and leukotrienes

Question 12

Explain what happens in the Delayed phase of Type I hyper.

Answer 12

late (hrs) : chemokines and cytokines (IL-4, IL-5, IL-8, IL-9,IL-3, GM-CSF, TNFα) –> attract inflammatory cells (e.g. eosinophils) and other mediators from mast cells –> inflammation and tissue damage

Question 13

Sensitization in type I hypersensitivity involves Class switcing to ———- production on first contact to Allergen

Answer 13

IgE

Question 14

Explain how Sensitization occurs on first contact w/allergen in type I hyper.

Answer 14

Upon first exposure to allergen -> Activation of TH2 (T-helper 2 cells) cells –> Promots the growth of B-cells –> Enhances Class switching to IgE through IL-4 production

• NOTE: mast cells express high levels of FcεRI, which mediate the response to allergens (Causing degranualtion)

Question 15

Fxn of Interleukin-4 (IL-4)?

Answer 15

induces the diffrentiation of T cells to TH2 cells –> promote the growth of B-cells -> Enhances class switching to IgE

* Part of Type I hypersensitivity

Question 16

Effector cells involved in type I hyper.?

Answer 16

mast cells, eosinophills and basophils

Question 17

Which Interleukins promote IgE production by B-cells?

Answer 17

IL-4 , IL-13

Question 18

Test used to detect allergic specific IgE in type I hypersensitivity

Answer 18

Skin test (wheal and flare response- takes min)

Question 19

Mucosal tissues are more prone to producing ——- responses

Answer 19

TH2

Question 20

what is responsible for the CM of Type I hyper?

* CM: clinical manifestations

Answer 20

Histamins, Tryptase and Leukotriens
(which are released in response to FcεRI cross-linking)

Question 21

first cells that respond to allergens?

Answer 21

Mast cells

* histamine is released within min of mast-cell activation

Question 22

fxn of Histamine?

Answer 22

1) Vasodilation
2) Increased mucous secretion
3) increased vascular permeability
4) Contraction of GI and bronchial SM

Question 23

Primary and secondary mediators released in response to cross-linking IgE-FcεRs by allergen on mast cell, eosinophils nad basophils

* type I Hypersensitivity

Answer 23

• Primary–> histamins, tyrptase and heparin (inflammatory cytokines)
• Secondary mediators –> Conversion of arachidonic acid into prostoglandins and leukotrines (inflammatory mediators)

Question 24

which mediators are responsible for the major cause of asthma sysmptoms?

Answer 24

Leukotrienes (LTC4, LTD4,LTE4) and prostoglandins (PGC2, PGE2)

Question 25

cytokine that recruits and activates eosinophils

Answer 25

IL-5

Question 26

Cytokine that stimultes Th2 responses to increase IgE production by B cells?

Answer 26

IL-4, IL-13

Question 27

Cytokine that attracts neutophils and other immune cells to the site of hypersensitivty (chemotactic factor)?

Answer 27

IL-8

Question 28

Cytokine that contributes to shock/ sepsis in systemic anaphylaxis

Answer 28

TNFα

Question 29

The consequences of IgE-mediated mast cell activation depend on the dose of antigen and its ———- of entry

Answer 29

Route of entry (GI, blood vessels, eyes, nasal passage)

Question 30

*Hyygeine hypothesis

Exposure to pathogens early in life provides a better T-cell balance and avoids dominance of ———- , which promotes ————— production by B cells

Answer 30

Th2, IgE
* IgE stimulates allergic response
* If we have low TH2 then we have TH1 cell dominance (when one increases the other decreases and vice verca)

* Hygeine hypothesis invloves TH1 cell dominance

Question 31

How does Desensetization treat Type I hyper?

Answer 31

↓IgE, ↓ TH2, ↑IgG, ↑ regulatory T-cells and their cytokines