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Path Week 2 > I - Allergy > Flashcards

I - Allergy Flashcards

(48 cards)

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1
Q

define allergy

A

immunological process that results in immediate and reproducible symptoms after exposure to an allergen

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2
Q

what type of reaction in allergy

A

type 1 hypersensitivity igE mediated

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3
Q

what is sensitisation

A

detection of specific IgE by skin prick testing or in vitro blood tests

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4
Q

does sensitisation or allergy occur more often

A

sensitisation +++

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5
Q

how does immune response to bacteria/virus/fungi differ from response to worms/venoms/proteases

A

immune reaction to worms/vemons respond to loss of tissue function, whereas bacterial immune reaction is due to response to direct pathogen

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6
Q

what are the signalling cytokines in Th2 immune response

A

IL25, IL33, TSLP

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7
Q

what are the effector cytokines in Th2 immune response

A

IL5, IL9, IL4, IL13

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8
Q

risk factor for development of IgE ABs

A

defects in skin epithelium (eczema)

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9
Q

describe pathway of Th2 immune response

A

damage epthelial cells secrete IL25/IL33 which act on tissue immune cells (DC, basophils etc)
induces Th2 cell immune response (IL4, IL5 etc)
and sensory neurons (itching)

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10
Q

when is IL4 induced in Th2 immune response

A

peptide MHC presentation to naive/memory Th2 cells

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11
Q

what causes immediate symptoms in allergy

A

release of inflamm mediators following allergen cross linking of IgE on surface of mast cells / basophils

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12
Q

what causes delayed symptoms in allergy

A

CD4 TH2 cell cytokine secretion and eosinophilic related tissue damage

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13
Q

what 4 factors promote IgE production

A

antigen dose
length of exposure
physical properties of allergen - eg assoicated w carrier proteins, linked to chitin, resistant to heat
route of exposure - resp/skin promotes IgE

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14
Q

what causes immune tolerance to food (prevent food allergy)

A

oral exposure to food
formation of anergic CD4 T cells lacking inflamm capacity to cause pathology
however they produce T reg cells that suppress tissue damage

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15
Q

what causes food allergy

A

skin / resp exposure to food, causing IgE sensitisation

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16
Q

describe the trends of the allergy epidemic

A

plateau of grass pollen / paeds asthma from 2000s ish to now
increase in red meat allergy recently

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17
Q

give 4 reasons why allergic disorders have risen over the last 150 years

A

hygiene hypothesis - decreased exposure = decreased natural immunity
increase in epithelial damaging agents due to industrialisation
loss of symbiotic relationship with bacteria
dietary changes

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18
Q

how do you diagnose allergy

A

HISTORY !!!
examination
allergen specific IgE test - eg skin prick / IgE blood test
functional allergen test

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19
Q

what allergies occur in infants

A

atopic dermatitis
food allergu

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20
Q

what allergies occur in childhood

Study These Flashcards
A

asthma
allergic rhinitis

21
Q

what allergies occur in adults

Study These Flashcards
A

drug
bee
occupational

22
Q

Sx of IgE allergies inc time frame

Study These Flashcards
A

minutes or up to 2-4 hours post allergen exposure
angioedema, urticaria, itching, cough, SoB, sneeze, N&V, hypotension, sense of impending doom

23
Q

how many organ systems are involved in an allergy

24
Q

what is a key feature of allergy that excludes allergy if its not present

Study These Flashcards
A

reproducible - after EVERY exposure

25
is the presence of IgE sufficient for diagnosis of allergic disease
NO - it is necessary for diagnosis but not diagnostic in itself
26
does the result of skin prick test determine severity of reaction
NO
27
what is involved in the skin prick test
expose patient to standardised solution of allergen extract through a skin prick to forearm positive control = histamine negative control = saline measure size of reaction to each
28
what is a positive result on skin prick test
wheal >3mm bigger than negative control
29
3 advantages of skin prick test
quick (15-20 mins) cheap negative predictive value >95%
30
3 disadvantages of skin prick test
requires experience to interpret risk of anaphylaxis 1 in 3000 high false positive rate
31
benefits of intradermal tests vs skin prick
more sensitive can be used to follow up venom / drug allergy if negative in SPT
32
cons of intradermal tests vs skin prick
less specific labour intensive greater risk of anaphylaxis
33
IgE AB blood test limitations
can detect IgE ABs with little clinical relevance low abundance allergen leads to reduced sensitivity limited clinical utility
34
when is component resolved diagnostics used
food allergy insect allergy guide immunotherapy
35
what % of peanut allergy persists after childhood
80%
36
what % of egg/milk allergy is outgrown
80%
37
when should blood sensitisation tests be done
Hx anaphylaxis can't stop antihistamines no access to SPT
38
name a potential new blood biomarker for anaphyalxis
mast cell tryptase
39
what is the gold standard for food and drug allergy Dx
challenge test - increasing volume of allergen ingested and response watched
40
limitations of challenge tests
risk of anaphylaxis difficult to interpret mild Sx needs close medical supervision
41
defining features of anaphylaxis
acute onset of symptoms / signs (mins to hours) severe / life threatening ABC problems skin and mucosal signs
42
incidence of anaphylaxis
1.5 to 8/100,000
43
age peak for anaphylaxis
0-4yrs
44
4 mechanisms of anaphylaxis (inc type, cells and mediators)
IgE - mast cells/basophils - histamine/PAF IgG - macrophages/neutrophils - histamine/PAF complement - mast cells/macrophages - histamine/PAF pharamcological - mast cells - leukotrienes/histamine
45
how can anaphylaxis be retrospectively diagnosed
serial serum tyrptase at 30 mins then 24hours
46
Mx of anaphylaxis
position - supine, legs raised IM adrenaline anti histamines after ABC repeat IM adreanline & give IV fluids if no response call for ITU help
47
what 3 receptors does andrenaline act on
alpha 1 beta 1 beta 2
48
safety netting for anaphyalxis
recognition of symptoms avoidane of triggers epi pen

Path Week 2 (18 decks)

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