hypersensitivity Flashcards
type 1 hypersensitivity reaction
allergic - immediate
what is the definition of allergy
IgE mediated antibody response to an external antigen
what is the hypothesis for the reason of inc prevalence of allergy
hygiene hypothesis
where do mast cells reside
tissues
what preformed substances do mast cells produce
histamine, tryptase and heparin
what substances do mast cells synthesise on demand
Leukotrienes, prostaglandins, cytokines including IL4 and TNF
what effect do mast cells have
inflammatory cascade
- inc blood flow
- SM contraction
- inc vascular permeability
- inc secretions at mucosal surface
what are the functions of mast cells
important in defence against parasites, and wound healing
what receptors do mast cells express
Fc receptor
what is extrinsic asthma
response to external antigen
what is extrinsic asthma mediated by
IgE
what is the clinical manifestation of bronchoconstriction
wheeze
what is the clinical manifestation of mucosal oedema and inc secretion
sputum production
why is sputum often yellow
Infiltration of lymphocytes and eosinophils into bronchioles
what are some other names for urticaria
hives
nettle rash
blisters
what is angioedema
Self-limited, localised swelling of subcutaneous tissues or mucous membranes
is angioedema pitting oedema
no
CF of anaphlaxis
sense of impending doom hypotension urticaria itch diarrhoea and abdo pain arrhythmia flush and sweat
can mast cells degranulate spontaneously
yes
what can u get urticaria in response to
pressure or heat
what drugs can cause mast cell degranulation
morphine and other opiates
aspirin and NSAIDs
what is samters triad
asthma, nasal polyps and salicylate sensitivity
what is aspirin induced asthma treated with
CysLt receptor antagonists
eg montelukast
what is aspirin indued asthma triggered by
aspirin and also other classical NSIDs (diclofenac and ibuprofen)
how would you test for anaphylaxis
evidence of mast cell degranulation - serum tryptase
what is the gold standard test for support a allergy diagnosis
skin prick test
what should be stopped 48 hours before a skinprick test
antihistamines
what other allergy investigations are available
specific IgE test and challenge test
specific IgE test
measure amount of IgE in serum against specific allergen
is total IgE useful in the diagnosis of allergic disease
no
in anaphylaxis what is the rise in tryptase proportional to
the drop in BP
what is sodium cromoglycate
a mast cell stabiliser
how is sodium cromoglycate used
topical spray
who is sodium cromoglycate used in
kids especially
what is symbicort
budesonide and formoterol
what is serotide
fluticasone and salmeterol
what is anaphylaxis managed with
self injectable adrenaline
what effect does adrenaline have
act on B2 ADR to constrict arterial SM
- inc BP there by limiting vascular leakage
- dilates bronchial SM thereby dec airflow obstruction
what is immunotherapy
controlled exposure to inc amounts of allergen
what are type II hypersensitivity reactions
direct cell killing
type II hypersensitivity
antibody binds to cell surface antigen activating complement and causing opsonisation
type II hypersensitivity - what do B cells produce
IgM or IgG antibody against membrane protein - bind to cell surface antigen
what is involved in the classical complement pathway
CI 2 and 4
what is the main complement pathway thing
C3
what does C3 activate
MAC
what can MAC do
direct killing of encapsulated bacteria by punching holes in bacterial cell membranes
what does C3 do - 3 things
chemotaxis
solubilisation of immune complexes
opsonisation
chemotaxis
inc vascular permeability inc the traffic of ells to the site of infection
what do opsonins act as
bridge between pathogen and receptor
what can complement fragments act as
opsonins - C3b
what is an example of type II hypersensitivity
transfusion ABO reaction
what is immediate haemolytic transfusion reaction
overwhelming systemic inflammatory response
what is autoimmune haemolytic anaemia
antibodies bind to red cells
what is Idiopathic thrombocytopaenic purpura
antibodies bind to platelets
what is goodpastures syndrome
antibodies bind to glomerular basement membrane
what is myasthenia gravis
antibodies bind to ACh receptor
what is guillan barré
antibodies bind to perisperhal nerve glycoprotein
what is graves disease
antibodies bind o TSH receptor
what is pemphigus vulgaris
antibodies bind to epithelial cell cement
what diseases may be transferred to neonate
myasthenia gravis, idiopathic thrombocytopaenic purpura, Rhesus disease
how do u manage type II hypersensitivity reactions
plasmapheresis - removal of pathogenic antibody
what is type III hypersensitivity reaction
immune complex mediated
type III hypersensitivity reaction
generalised reaction resulting from immune complex deposition in blood vessel walls, skin joints and glomeruli where they cause a chronic inflammatory response
III hypersensitivity reaction example
farmers lung
what are the agents of farmers lung
Aspergillus fumigatus
Micropolyspora faeni
what are the agents in bird fanciers lung
Avian serum proteins
what are the agents in malt workers lung
aspergillus clavatus
what are the agents in cheese workers lung
Aseprgillus clavatus
Penicillum casei
what are the agents in maple bark strippers lung
Cryptostroma corticale
what causes breathlessness in hypersensitivity pneumonitis
Alveolitis, caused by activated phagocytes and complement – results in decreased efficiency of gas transfer
what is SLE
antibodies produced against the contents of cell nuclei, form immune complexes which are deposited etc
what does complex deposition in joints result in
arthralgia
what does deposition of IgG immune complexes in glomeruli cause
renal dysfunction
what does immune complex in skin cause
vasculitic purpura
how do u diagnose type III reactions
specific IgG to putative antigen
how does one manage type III reactions
dec inflammation - corticosteroids
dec antibody production - IS
type IV
delayed
what cell mediates type IV
T cell
what is the pathophysiology of type IV
initial sensitisation to antigen primes the T cells
subsequent exposure activates the primed T cells which recruit other cells and release enzymes
an example of type IV
nickel hypersensitivity
non autoimmune type IV diseases
TB, sarcoidosis, leprosy, cellular rejection of solid organ transplant
autoimmune type IV diseases
diabetes, psoriasis, rheumatoid arthritis
what is a granuloma
organised collection of activated macrophages and lymphocytes