Mechanisms of Allergy Flashcards
What does Allos and Ergon mean?
Allos - other
Ergon - reactivity
Triggers:
Most common food causes? - 3
Common drug causes?
Venom - from which bugs?
Other materials?
Nuts (peanut, tree nut)
Fish, shellfish
wheat, soya, sesame, milk
Penicillin - amoxicillin
Bees and wasps
Latex
Contrast media
Topical products such as hair dye and salicytes
Explain type 1 hypersensitivity?
Mediated by IgE antibodies and causes immediate reactions including anaphylaxis and allergy
Mediated by IgE antibodies released from mast cells and basophils
Type 1 hypersensitivity - what are the 3 phases?
Sensitization
Immediate phase reaction
Late Phase Reaction
(1) Sensitisation:
- What occurs?
Allergens pick up by antigen presenting cells (such as DCs).
They are taken up and presented on surface - MHC I
Presented to NAIVE T cells
NAIVE T cells activated to T HELPER cells which activate B cells
B cells produce IgE
IgE binds to surface.
NOTHING HAPPENS UNTIL YOU COME INTO CONTACT WITH ALLERGEN AGAIN
(2) Immediate phase reaction:
- What happens?
IgE primed for allergen
Cross linking of IgE on mast cell surface
Mast cell degranulation
Release of histamine and TRYPTASE
What are the effect of histamine release?
- Lungs
- Mucous
- Heart
- Arteries
- Veins
- Capillaries
Bronchoconstriction
Mucous secretion
Reduce cardiac contractility
Vasoconstriction: reduce blood to tissues
Venodilation: reduced blood to heart
Increased vascular permeability
Respiratory symptoms - 3
CV - 3
GI - 3
Central nervous system - 4
SOB
Wheeze/stridor
Chest tightness
Can also complain of lump in their throat
Tachycardia
Hypotension/collapse
Cardiac arrest
Abdo pain
N&V
Diarrhoea
‘Feeling of impending doom’
headache
altered mental status
confusion, drowsiness
(3) Late phase reaction:
- Why does this happen?
T helper 2 cells - newly recruited eosinophils and basophils - secrete pro-inflammatory mediators
Cytokines and chemokine in late phase
Just know they is a BIPHASIC reaction
