Type 1 Hypersensitivity Flashcards
Which antibody class mediates Type 1 Hypersensitivity?
IgE
What is another name for Type 1 Hypersensitivity?
Immediate hypersensitivity
In order for immediate hypersensitivity, a host must have what?
Pre-existing IgE antibodies against the allergen
FcER receptors are found on which cells, and for how long?
Mast cells (months)
Eosinophils (days to weeks)
Basophils (days)
What are the features of Type 1 allergens?
1) Small, soluble proteins
2) Multivalent (multiple identical epitopes)
3) Present at low doses
Which cytokines are involved in the sensitization phase of Type 1 hypersensitivity?
Th2 cytokines
a) IL-4 - class-switch to IgE
b) IL-5 - eosinophil activation
c) IL-13 - mucus
What are the primary mediators of Type 1 hypersensitivity and what are their effects?
1) Histamine and Serotonin
2) Contraction of respiratory and intestinal smooth muscle, relaxation and increased permeability of blood vessels
What are the secondary mediators of Type 1 hypersensitivity and what are their effects?
1) Leukotrienes/prostaglandins
- Increase vascular permeability, contract pulmonary SM
2) Cytokines (TNFa and IL-4)
What are the 3 basic symptoms of Type 1 hypersensitivity (not all 3 may be present)?
1) Diarrhea and vomiting (GI)
2) Coughing (Respiratory)
3) Edema (Vasculature)
What causes a wheal and flare reaction?
Histamine
Wheal = swelling due to plasma leakage
Flare = engorgement of dilated vessels with RBCs
What is a late phase reaction, what triggers it, and what stops it?
a) Inflammation 2 to 6 hr. after exposure
b) Caused by accumulation of eosinophils and other inflammatory leukocytes
c) Corticosteroids (inhibit cytokine synthesis), NOT histamine
What are 4 types of Type 1 Hypersensitivity?
1) Rhinitis
2) Asthma
3) Food allergies
4) Dermatitis
What causes asthma, and which species can have it?
Chronic inflammation (constriction and increase mucus come-and-go in presence of allergen)
Cats
Do food allergies cause systemic anaphylaxis in animals?
No
What do antihistamines treat?
Runny noses
Which 2 drugs treat asthma, which is for humans, and which is for cats?
Antileukotrienes (humans)
Corticosteroids (cats)
What is epinephrine used for, and how does it work?
Treating systemic anaphylaxis. It relaxes bronchial muscles and decreases degranulation by increasing cAMP.
What is Cytopoint (lokivetmab) used for and how does it work?
Used for canine Type 1 dermatitis.
It’s a monoclonal antibody that neutralizes IL-31 to reduce inflammation.
What is Xolair(omalizumab) used for and how does it work?
Treats asthma in humans. It’s a monoclonal antibody that binds the Fc region of IgE so it can’t reach mast cells.
What are the two effects of allergen immunotherapy?
1) Shifts from IgE to IgG
2) Suppresses Th2 response
What is the main content of eosinophil granules, and what does it do?
Major basic protein; kills helminths (and host tissue)
