Immuno 6: Allergy Flashcards
Name 1 cytokine released from damaged epithelium secondary to exposure to an allergen/worm ?
TSLP
Which T cells are involved with allergy response ?
Th2 cells
List 3 important cytokines released by Th2 cells in an allergic response ?
IL-4
IL-5
IL-13
Which cytokine released by Th2 cells is considered the master switch that causes Isotype switching of B cellls to IgE ?
IL-4
How do allergens/worms cause Histamine and leukotriene release ?
They cause cross linking of IgE receptor on mast cells, which causes release of Histamine and leukotriene
Oral exposure to allergens promotes…….
Immune tolerance with IgG and IgA
Skin and respiratory exposure to allergens promotes……..
IgE sensitisation
Which allergies develop in infants ?
Allergic dermatitis
Food allergies - milk, egg, nuts
Which allergies develop in children ?
Asthma
allergic Rhinitis
Which allergies tend to develop in adults ?
Drug allergies
Oral allergy syndrome
Occupational allergies
Bee sting allergy
Name a bio marker for anaphylaxis?
Mast cell tryptase
is useful in anaesthetics to rule out anaphylax when there is acute hypotension and rash
What is the gold standard test for food and drug allergy ?
Challenge tests
Give 3 different types of anaphylaxis other than IgE ?
IgG- e.g monoclonal antibodies
Complement- dialysis membranes
Pharmacological- aspirin and NSAIDS
What is a cause of Throat swelling which mimics anaphylaxis ?
C1 inhibitor deficiency
What is the most important treatment of Anaphylaxis ?
IM adrenaline
What is a cause of delayed food induced anaphylaxis ?
Beef, pork,lamb
Tick bites
Gelatine in vaccines can do it as well
describe the Th2 mediated response
stressed/damaged epithelium releases signalling cytokines eg TSLP
these cytokines act on Th2 cells, Th 9 cells and ILC2 cells
promoting the selectionof IL4, IL5, IL13
these act on eosinophils and basophils
TSLP and other cytokines also activate follicular Th2 cells which releases IL4
IL4 stimulated B cells to produce IgE and IgG4
skin dendritic cells promote the secretion of Th2 cytokines
describe mast cell mediated allergy response
allergen causes mast cell cross linking of IgE
causes release of histamine, prostaglandins, leukotrienes
act on the endothelium - increased permeability, smooth muscle contraction, neuronal stimulation (itch)
what happens when an allergen is ingested through the oral route
Tregs derived from the GI mucose will inhibit IgE sythesis to keep the immune system in balance
what are the clinical features of an IgE mediated response
minutes to hours after exposure
angioedema, urticaria, flushing, itching, cough, SOB, nasal congestion, wheeze, red watery eyes, d+v, hypotension
usually at least 2 organ systems involved
symptoms are reproducible
allergic symptoms can be triggered by cofactors
how can we investigate allergic disease
skin prick and blood test lab measurements of allergen-specific IgE component-resolved diagnosis basophil activation test challenge test
during an acute episode - serial mast cell tryptase
blood and/or urine antihistamine
describe specific IgE sensitisation tests
skin prick and blood tests
higher concentration = more symptoms
higher affinity to target = increased risk
how does the skin prick test work
positive control (histamine) negative control (diluent) inject a standardised solution of allergen positive test = wheal >3mm greater than negative control antihistamines to be discontinued for 48 hrs before the test
describe the serum specific IgE blood test
allergen bound to a sponge and the specific IgE will bing to the allergens
washed over with anti-IgE antibody tagged with fluorescent label
what is mast cell tryptase a marker of
anaphylaxis
tryptase = pre-formed protein found in mast cell granules
systemic degranulation of mast cells during anaphylaxis results in increased serum tryptase
peak conc = 1-2 hrs
baseline = 6-12 hrs
what is the gold standard test for food and drug allergy diagnosis
challenge test
increasing volumes of offending food/ drug ingested
double blind placebo or open challenge
risk of severe reaction
what is the basophil activation test
measurement of basophil response to allergen IgE cross linking
activated basophils increase the expression of CD63, CD203, CD300 protein on their cell surface
features of anaphylaxis
severe potentially systemic hypersensitivity reaction
rapid onset, life-threatening airway
breathing and circulation problems
skin is the most frequent organ involved
mechanisms of anaphylaxis
IgE - mast cells, basophils - histamine + PAF
- food, insect venom, ticks, penicillin
IgG - macrophages, neutrophils - histamine + PAF
complement - mast cells, macrophages - PAF + histamine
- biologicals, blood and IgG transfusions
pharmacological - mast cells - leukotrienes + histamine
- NSAIDs including aspirin, opiates, neuromuscular and quinolones
complement - lipid excipients, liposomes, dialysis membranes and PEG
how is anaphylaxis managed
IM ADRENALINE 100% oxygen fluid replacement inhaled bronchodilators hydrocortisone 100mg IV chlorpheniramine 10mg IV
difference between food allergy and food intlerance
allergy = adverse effects arising from specific immune response that occurs reproducibly on exposure to a given food
intolerance = non-immune reactions that include metabolic, pharmacological and unknown mechanisms
