Type I Hypersensitivity Flashcards
Type 1 hypersensitivity
- humoral immune respone
- allergies or asthma
- exaggerated Th2 response
- Excessive amount of IgE=Atopy
- affected animals=atopic
- genes + envir. factors = allergies
- susceptible breeds
- human child infection
- early contact w/ allergens
- intestinal microflora, parasite worms
Overproduction of which antibody?
IgE
IL-4 overproduction, therefore
increase Th2 activation & B cell stimulation
FceR has ___ affinity & ___ binding
increased & irreversible binding
Where is FceRI present?
Mast cells, basophils, neutrophils, eosinophils, macrophages & dendritic cells
Where is FceRII present?
B cells, NK cells, macrophages, dendritic cells, eosinophils & platelets
3 main components
IgE, Mast Cell & antigen/allergen
Is there a rxn seen after first exposure?
no
The allergy loop dendritic cells express trimeric FceRI and as a result can bind antigen-
IgE complexes.
-stimulates Th2 –> secrete cytokines
FceRI
- high affinity
- mast cell degranulation
- eosinophil ADCC
- dendritic cells
- macrophages
FceRII
- low affinity
- B cell down regulation
- macrophage phagocytosis
- NK cell
- Dendritic cells
- eosinophils
Mast Cell
- located in intestine, skin, airways, nerves, blood vessels
- release pro-inflammatory mediators
Connective tissue/skin mast cells
- histamine
- Heparin
- lifespan 6,
Intestine/lung mast cells
- chondroitin sulfate
- few histamine
- lifespan <40 days
Granules have ___ molecules
proinflammatory
Seconds
Granule Exocytosis
- histamine
- serotonin
- tryptase
- kalikreins
- proteases
- proteoglycans
Minutes
Eicosanoid Synthesis & Secretion
- Leukotrienes
- Prostaglandins
- Platelet activating factors
Hours
Cytokine Synthesis and Secretion
-IL-4,5,6,13
TNF alpha
MIP 1alpha
Mast Cells
IL-6
IL-13
(degranulation in presence of IgE)
Basophils
IL-3,4,6,13
Histamine
GM-CSF
(basophil differentiation in bone marrow)
Eosinophils
IL-8
Degranulation
(terminal effector cells of allergic responses)
Th2 cells
IL-5
IL-13
(Eotaxins)
Factors of ganules have effects on
GI tract, respiratory tract, blood vessels
Enhance mast cell degranulation
stimulation of adrenoreceptors -Norepinephrine -Phenylephrine -block Beta adrenoreceptors Propranol
Inhibition of Mast cell degranulation
blocking of adrenoreceptors
- stimulate Beta adrenoreceptors
- isoproterenol
- epinephrine
- salbutamol
Immediate inflammation time Vs late phase rxn
10-20 minutes
6-12 hours
Mast cells
alpha receptor stimulation:
beta receptor stimulation:
- enhances degranulation
- suppresses degranulation
Smooth muscles
alpha receptor stimulation:
beta receptor stimulation:
- contracts
- relaxes
Blood vessels
alpha receptor stimulation:
beta receptor stimulation:
- constricts
- dilates
Clinical type I hypersensitivity examples
- allergic anaphylaxis
- milk allergy
- food allergy
- allergies to parasites
- atopic dermatitis
The most common body system usually affected is the
respiratory system
liver in dogs
Allergic anaphylaxis is serious why?
life threatening
Dx of Type I hypersensitivity
- intradermal skin testing
- passive cutaneus anaphylaxis
- measuring IgE
Atopic Dermatitis
allergen, IL-31, sensory neurons cause itching
Tx of type I hypersensitivity
- avoid exposure
- corticosteroids/antihistamines
- beta stimulants: epinephrine
- alpha antagonists: methoxamine
- allergen specific immunotherapy
Immunotherapy
- injections, oral drops
- increase production of IgG antibodies
- main antibody involved is IgE, IgE & IgG will compete for antigen and eliminate antigen faster
Atopic Dermatitis tx
block the IL-31 which will stop itching but not the allergen
Allergen
antigen that can trigger type I hypersensitivity
If the rate of release of vasoactive molecules from these mast cells exceeds its ability to adjust to the rapid changes in the vascular system, an animal will undergo allergic anaphylaxis and may die. T/F
TRUE
