tyoe 1 hypersensitivity Flashcards
Hypersensitivity Reactions
Activation of immune system in the absence of a danger
Resulting in tissue damage, discomfort and even death
Type 1 Hypersensitivity
immediate HSR
Type 1 Hypersensitivity Immune Reactant
IgE
Type 1 Hypersensitivity Antigen
Soluble antigen
Type 1 Hypersensitivity Effector Mechanism
Mast-cell activation
Type 1 Hypersensitivity Examples
allergic rhinitis, asthma, system anaphylaxis
Allergen
a stimulus
Harmless environmental substance that induces an allergic response
Anaphylaxis
A rapidly progressing allergic reaction, could be life-threatening
Atopy
Familial predisposition
Initiating cells
APC, Th0, Th2 and B cells
Common Allergens
Low molecular weight proteins
Must contain peptides that bind to host MHC Class II molecules
Favor activation of IL-4 producing Th2
IgE
very low serum concentrations
Fc region binds to the FcϵR on the effector cells
Sensitization phase
IgE antibody bind to mast cells, basophils and eosinophils via FcϵR1
Activation phase
Re-exposure to an antigen cross links cell bound IgE and activates mast cells to degranulate
Effector phase
many pharmacologically active agents released by the mast cells and basophils
Tho -> Th2
IL-4
B cell -> Th2
IL-4
IL-13
Th2 -> Eosinophil
IL-5
recruit eosinophils to tissue of reaction
CCL11
Mast cells can be activated by
PRR such as Toll like receptors
Fc receptor for IgA and IgG
C5a, C3a, C4a
Chemicals (drugs)
Stress
inhinbits COX
aspirin
Systemic anaphylaxis
allergens reaching the blood steam
Inhaled antigens: Asthma
cute response in allergic asthma leads to Th2 mediated chronic/late inflammation of the air way
TGF beta promotes
class switch to IgG/IgA
Diagnosis of Type I HSR
Skin test:
Wheal and Flare Reaction
2. RAST: RadioAllergoSorbent Test (detects allergen specific IgE) - no IgE = no allergy
- Tryptase and histamine serum level:
Anaphylaxis
(pharmalogical treatment) Prevent IgE mediated mast cell degranulation
Sodium cromoglycate
(pharmalogical treatment) Block mediators by blocking receptors
Anti-histamines
(pharmalogical treatment) Reverse the action of mediators
Epinephrine
(pharmalogical treatment) Anti-inflammatory agents
Steroids – nasal spray
Immunological treatment
Desensitization
Monoclonal antibodies
Correction of Th1/Th2 balance
Desensitization
Allergy shots
Correct isotype switch from IgE to IgG
Monoclonal antibodies
Anti IL-4, IL-13, IL-5 and IgE
Omalizumab (IgE specific)
Mepolizumab (IL-5 specific)
