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Immu > Immu 5: Allergy > Flashcards

Immu 5: Allergy Flashcards

1
Q

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

A

TSLP

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2
Q

describe the Th2 mediated response

A
  • 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
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3
Q

Which T cells are involved with allergy response ?

A

Th2 cells

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4
Q

Which T helper cells recognise pathogen structures like PAMPs? (2)

A

Th1 and Th17

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5
Q

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

A

IL-4
IL-5
IL-13

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6
Q

3 lymphocyte cell types involved in initial allergen response

A
  • Th2 cells
  • Th9 cells
  • ILC2 cells
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7
Q

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

A

IL-4

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8
Q

What protein on the surface of dendritic cells signals to naïve T cells in food allergy?

A

OX40

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9
Q

How do allergens/worms cause Histamine and leukotriene release ?

What is the effect of these mediators?

A

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

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10
Q

Oral vs skin / resp exposure to allergen

A
  • Oral: IgG and IgA mediated sensitisation
  • Skin/resp: IgE sensitisation
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11
Q

what happens when an allergen is ingested through the oral route

A

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

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12
Q

Which allergies develop in infants ? (2)

A

Atopic dermatitis
Food allergies - milk, egg, nuts

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13
Q

Which allergies develop in children ?

A

Asthma
allergic Rhinitis

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14
Q

Which allergies tend to develop in adults ? (4)

A

Drug allergies
Oral allergy syndrome
Occupational allergies
Bee sting allergy

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15
Q

Name a bio marker for anaphylaxis?

What is peak concentration?

What releases this marker?

A

Mast cell tryptase

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

Peak concentration = 1-2 hours after exposure

Systemic degranulation of mast cells during anaphylaxis results in increased serum tryptase

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16
Q

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

A

Challenge tests

  • can be done in clinic to see if food or drugs promotes an allergic response
17
Q

Give 3 different types of anaphylaxis other than IgE ?

A

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

18
Q

What is a cause of Throat swelling which mimics anaphylaxis (rare)?

A

C1 inhibitor deficiency

19
Q

What is the most important treatment of Anaphylaxis ?

A

IM adrenaline (outer aspect of thigh)

20
Q

how is anaphylaxis managed

A
  • IM ADRENALINE
  • 100% oxygen
  • fluid replacement
  • inhaled bronchodilators (salbutamol)
  • hydrocortisone 100mg IV
  • chlorpheniramine 10mg IV
21
Q

What is a cause of delayed food induced anaphylaxis ?

A

Beef, pork,lamb
Tick bites

Gelatine in vaccines can do it as well

22
Q

what are the clinical features of an IgE mediated response

A
  • 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
23
Q

how can we investigate allergic disease

A
  • 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
24
Q

Describe specific IgE sensitisation test

What is a +ve test?

Rule with antihistamines before doing this test?

A

Skin prick and blood tests

  • higher concentration = more symptoms
  • higher affinity to target = increased risk
  • Measure the local wheal and flare response to controls and allergens

+ve test = wheal ≥ 3mm greater than the negative control

Antihistamines: stop these 48 hrs before test (do serum IgE levels if they cannot stop this for whatever reason)

25
Q

Do Skin prick and blood tests determine allergy?

A

No - a positive IgE test only demonstrates sensitisation, NOT clinical allergy (i.e. IgE is a risk factor for allergy, it is not synonymous with allergy)

26
Q

how does the skin prick test work

A
  • 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
27
Q

describe the serum specific IgE blood test

A

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

28
Q

what is the basophil activation test

A
  • measurement of basophil response to allergen IgE cross linking
  • detect food allergy
  • activated basophils increase the expression of CD63, CD203, CD300 protein on their cell surface
29
Q

mechanisms of anaphylaxis

A

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

30
Q

difference between food allergy and food intlerance

A

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

31
Q

A 15-year-old boy with a history of asthma and hayfever who notices an urticarial and angioedema skin rash shortly after eating peanuts. What is the most appropriate initial diagnostic test?

A

Skin prick test

32
Q

Test that can be done to detect IgE to single protein components, especially useful for peanuts and allergies so that you don’t have to do challenge test

A

Component Resolved Diagnostics (CRD)- A.k.a. Radioallergosorbent Test

33
Q

A 55-year-old man who attends A&E with angioedema involving the lips and tongue which has developed over previous hours. He has a history of hypertension and is taking an ACEi and CCB. Clinical examination shows a pulse of 75bpm, BP of 150/90, RR of 18/min and O2 sats of 78% on air. What is the most likely diagnosis?

A

ACEi induced angioedema

34
Q

What does epipen contain in children and adults?

A
  • 300mg adrenaline- ADULT
  • 150mg adrenaline- CHILDREN
  • Prednisolone 20mg OD
  • Antihistamine (Cetirizine 10mg OD)
35
Q

What is oral allergy syndrome?

A
  • Limited to oral cavity, swelling and itch: only 1-2% cases progresses to anaphylaxis
  • Sensitisation to inhalant pollen protein lead to cross reactive IgE to food
  • Onset after pollen allergy established: affect adults > young children
36
Q

A 35-year-old man with tree pollen hay fever and immediate lip tingling and swelling immediately after eating apples. What is the most likely explanation for IgE hypersensitivity ?

A

Cross reactive IgE sensitisation between hay fever and apple allergens

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