Immuno 6: Allergy

Question 1

Name 1 cytokine released from damaged epithelium secondary to exposure to an allergen/worm ?

Answer 1

TSLP

Question 2

Which T cells are involved with allergy response ?

Answer 2

Th2 cells

Question 3

List 3 important cytokines released by Th2 cells in an allergic response ?

Answer 3

IL-4
IL-5
IL-13

Question 4

Which cytokine released by Th2 cells is considered the master switch that causes Isotype switching of B cellls to IgE ?

Answer 4

IL-4

Question 5

How do allergens/worms cause Histamine and leukotriene release ?

Answer 5

They cause cross linking of IgE receptor on mast cells, which causes release of Histamine and leukotriene

Question 6

Oral exposure to allergens promotes…….

Answer 6

Immune tolerance with IgG and IgA

Question 7

Skin and respiratory exposure to allergens promotes……..

Answer 7

IgE sensitisation

Question 8

Which allergies develop in infants ?

Answer 8

Allergic dermatitis

Food allergies - milk, egg, nuts

Question 9

Which allergies develop in children ?

Answer 9

Asthma

allergic Rhinitis

Question 10

Which allergies tend to develop in adults ?

Answer 10

Drug allergies
Oral allergy syndrome
Occupational allergies
Bee sting allergy

Question 11

Name a bio marker for anaphylaxis?

Answer 11

Mast cell tryptase

is useful in anaesthetics to rule out anaphylax when there is acute hypotension and rash

Question 12

What is the gold standard test for food and drug allergy ?

Answer 12

Challenge tests

Question 13

Give 3 different types of anaphylaxis other than IgE ?

Answer 13

IgG- e.g monoclonal antibodies
Complement- dialysis membranes
Pharmacological- aspirin and NSAIDS

Question 14

What is a cause of Throat swelling which mimics anaphylaxis ?

Answer 14

C1 inhibitor deficiency

Question 15

What is the most important treatment of Anaphylaxis ?

Answer 15

IM adrenaline

Question 16

What is a cause of delayed food induced anaphylaxis ?

Answer 16

Beef, pork,lamb
Tick bites

Gelatine in vaccines can do it as well

Question 17

describe the Th2 mediated response

Answer 17

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

Question 18

describe mast cell mediated allergy response

Answer 18

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)

Question 19

what happens when an allergen is ingested through the oral route

Answer 19

Tregs derived from the GI mucose will inhibit IgE sythesis to keep the immune system in balance

Question 20

what are the clinical features of an IgE mediated response

Answer 20

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

Question 21

how can we investigate allergic disease

Answer 21

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

Question 22

describe specific IgE sensitisation tests

Answer 22

skin prick and blood tests
higher concentration = more symptoms
higher affinity to target = increased risk

Question 23

how does the skin prick test work

Answer 23

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

Question 24

describe the serum specific IgE blood test

Answer 24

allergen bound to a sponge and the specific IgE will bing to the allergens
washed over with anti-IgE antibody tagged with fluorescent label

Question 25

what is mast cell tryptase a marker of

Answer 25

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

Question 26

what is the gold standard test for food and drug allergy diagnosis

Answer 26

challenge test
increasing volumes of offending food/ drug ingested
double blind placebo or open challenge
risk of severe reaction

Question 27

what is the basophil activation test

Answer 27

measurement of basophil response to allergen IgE cross linking
activated basophils increase the expression of CD63, CD203, CD300 protein on their cell surface

Question 28

features of anaphylaxis

Answer 28

severe potentially systemic hypersensitivity reaction
rapid onset, life-threatening airway
breathing and circulation problems
skin is the most frequent organ involved

Question 29

mechanisms of anaphylaxis

Answer 29

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

Question 30

how is anaphylaxis managed

Answer 30

IM ADRENALINE 
100% oxygen 
fluid replacement 
inhaled bronchodilators
hydrocortisone 100mg IV
chlorpheniramine 10mg IV

Question 31

difference between food allergy and food intlerance

Answer 31

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