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Immunology 6 - Hypersensitivity (i) (acute allergic reaction (wheezing,…
Immunology 6 - Hypersensitivity (i)
immune reactions
infection
protective immunity
recurrent infection
innocuous (non-harmful) substance
no response
allergy
grafted organ
acceptance
rejection
self
tolerance
autoimmunity
tumour
protective immunity
cancer
hypersensitivity
potent immune reaction leading to tissue damage
seen in allergy, autoimmunity + other immunopathologies
classification
type 1
IgE-mediated
rhinitis
asthma
eczema (becomes cellular)
urticaria
angioedema
anaphylaxis
laryngeal oedema
bronchospasm
shock
phases
1) sensitisation
1st exposure
extraction of antigen (APC)
activation of antigen-specific T cells
2) early/acute phase
IgE produced, binds to mast cells
dark granules store premade histamine (causes acute allergic reactions) + other inflamm mediators (e.g. IL4 to activate B cells) - fast release
increased vasc permeability, local swelling
3) late phase (2nd wave, more swelling)
type 2
Ig cytotoxicity
type 3
immune complex deposition (covalently bound to C3b)
type 4
delayed
cell-mediated
Allergen sources
inhaled
rarely cause anaphylaxis
pollen
animal dander
mold spores
faeces of v small animals (e.g. dust mites)
injected
often cause anaphylaxis
v short time to onset of symptoms, 5 mins to arrest
insect venom
drugs (therapeutic or not)
ingested
food
oral drugs
antigen diffuses into blood from gut (dissemination)
causes urticaria
smooth smooth contraction: nausea + vomiting
contacted
plants
industrial products (plant-derived or synthetic)
metals
often type 4 (cellulitis)
skin test
+ve + -ve controls
can't take antihistamines before test
on forearm, or back if child v young
acute allergic reaction
wheezing
urticaria
sneezing
rhinorrhoea
conjunctivitis
anaphylaxis
chronic allergic reaction
eosinophil attraction
longer + nearly as severe
harder to treat (sensitivity to steroids)
wheezing, nasal blockage, eczema
present in 50% of allergic asthmatics
also mediated by CKs
acute inflamm mediators
contract smooth muscle
increase mucus secretion from airway epithelium
increase vasc permeability
FEV1 of an asthmatic decreased in both immediate + late response
autoIgs
in many autoimmune diseases
e.g. Hashimoto's thyroiditis
most common cause of hypothyroidism
T-cell mediated tissue injury
anti-thyroid Igs
presence doesn't necessarily mean pathology, but useful in Dx