Type I Hypersensitivity: Allergy & Anaphylaxis

IgE

What is the main immune reactant for type I hypersensitivity reactions?

Mast cell activation

What is the effector mechanism for type I hypersensitivity reactions?

IgE and mast cells

What are at the center of type I hypersensitivity reactions?

Degranulation

When IgE binds to mast cells it promotes what?

Sensitized

Allergic reactions develop after an individual is exposed and _____________

Emptying

What effect does mast cell activation/degranulation have on the GI tract?

Difficulty breathing

What effect does mast cell activation/degranulation have on the respiratory tract?

Movement of fluids, proteins, and cells out of blood vessels and into inflamed tissues

What effect does mast cell activation/degranulation have on blood vessels?

A

T or F: Type I HS reaction responses are immediate because histamine is preformed

Granules (histamine, serotonin, etc.)

What is released within seconds of mast cell activation?

Eicosanoids (leukotrienes, prostaglandins, platelet activating factor)

What is released within minutes of mast cell activation?

Cytokines (IL-4 and IL-5)

What is released within hours of mast cell activation?

Small, soluble protein

Describe the nature of the antigen for type I HS

Mucosal or skin

What is the route of exposure for type I HS?

Th2

What is the predominant Th pathway for type I HS?

IL-4

This interleukin stimulates B cells to isotype switch and produce IgE

IL-5

Activates eosinophils in type I HS reactions

A

T or F: Activated mast cells stimulate additional IgE synthesis

A

T or F: Type I HS reactions work through signal transduction

Pro

Eosinophils in type I HS reactions play a (pro or anti) inflammatory role

1. Acute systemic anaphylaxis

2. Regional/localized urticarial and/or edema

3. Allergic dermatitis

4. Allergic gastroenteritis

5. Allergic rhinitis/conjunctivitis

What are the clinical manifestations of type I hypersensitivity?

Anaphylactic shock

If an allergen enters intravenously and connective tissue mast cells are activated, what results?

Localized response (hives)

If an allergen enters subcutaneously and connective tissue mast cells are activated, what results?

Allergic rhinitis and bronchospasm

If an allergen is inhaled, what results?

Diarrhea, vomiting and anaphylaxis

If an allergen is ingested, what results?

Hepatic veins (viscera)

What is the canine target organ for anaphylaxis?

Respiratory tract and intestine

What is the feline target organ for anaphylaxis?

Respiratory tract and intestine

What is the equine target organ for anaphylaxis?

Pulmonary edema and intestinal hemorrhage

Acute anaphylaxis could result in what?

Th2

Canine allergic dermatitis (Th1 or Th2) response

IL-4, IL-5, and IL-13

What interleukins are increased in skin lesions associated with canine allergic dermatitis?

IgE and IgG1

What immunoglobulins are increased due to canine allergic dermatitis?

II

Canine allergic dermatitis has increased MHC class (I or II) expression by Langerhans cells

A

T or F: Canine allergic dermatitis causes a decreased Treg function

Wheal and flare reaction

A skin reaction that may follow injection of an antigen

Wheal

Fluid filled raised area rather

Flare

Area of reddening spreading out from the site of antigen injection

1. Minimize exposure (prevention)

2. Minimize impact of exposure (pharmacological)

3. Desensitization

What are the three treatment strategies for canine allergic dermatitis?

Th2, Th1

With increasing doses of allergen the response will turn from a (Th1 or Th2) to a (Th1 or Th2)