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3 IIH > 10.1 Allergy > Flashcards

10.1 Allergy Flashcards

1
Q

Define hypersensitivity

A

reactions of the immune system that are detrimental to the host

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2
Q

Define allergy

A

a specific immune mechanism against an allergy (IgE)

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3
Q

Define Sensitisation

A

the immune system recognises allergen, but does not necessarily induce systemic symptoms

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4
Q

Define atopy

A

predisposition to allergic disease

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5
Q

Define anaphylaxis

A

a severe, life threatening, generalised or systemic IgE mediated reaction

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6
Q

Define anaphylactoid

A

systemic reaction, not IgE mediated. can be severe and life threatening

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7
Q

What is a type I hypersensitivity reaction?

What is it associated with?

A

IgE mediated mast cell degranulation and activated eosinophils

anaphylaxis
venom / drug / food allergy

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8
Q

What is a type II hypersensitivity mechanism?

A

self IgG antibodies bind antigens on patient’s own cell surfaces directly causing damage

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9
Q

Name a type of type II hypersensitivity mechanism

A

autoimmune haemolytic anaemia

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10
Q

What is a type III hypersensitivity mechanism?

A

immune-complex between circulating antigen and IgG causes damage

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11
Q

Name a couple of examples of type III hypersensitivity mechanisms

A

glomerulonephritis

Vasculitis

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12
Q

What might a type 4 hypersensitivity mechanism be otherwise called?

A

delayed hypersensitivity

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13
Q

What is a type 4 hypersensitivity mechanism?

A

cellular immune response mediated by T cells

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14
Q

Name an example of type 4 hypersensitivity

A

contact dermatitis

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15
Q

How would type I hypersensitivity present?

A

within minutes of exposure
patient often can say what caused it
may be life threatening

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16
Q

How would type

IV hypersensitivity present?

A

at least 4 hours, but often a day or 2 after exposure
more difficult to identify the antigen
nasty but not life-threatening

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17
Q

How might you investigate contact dermatitis?

A

patch testing

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18
Q

What problem is associated with patch testing?

A

could be irritant / allergic

gotta wait 5 days to see how that boi develops xxx

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19
Q

How might you diagnose type I allergy?

A

Serum specific IgE

Skin prick testing

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20
Q

What might indicate that the skin prick test is the wrong test to use?

A

the hypersensitivity is not IgE mediated

21
Q

What does a skin prick test diagnose?

A

sensitivity

may be allergic if consistent with symptoms

22
Q

What is the pathway to developing type I allergy?

A

allergen exposure
sensitisation
specific IgE production
RE-exposure to allergen - allergic response

23
Q

How much IgE is in the blood normally

A

not much at all

24
Q

What is required for class switching to IgE?

A

Th2 cytokines IL-4/13

25
Q

What does the extra constant region of IgE allow?

A

binding of allergy effector cells via FC-gamma-R1

26
Q

What key mast cell mediator is used to help diagnose anaphylaxis and why?

A

tryptase

lasts about 8 hours tbh

27
Q

Name 4 early phase mast cell mediators

A

histamine
kalikrein
serotonin
proteases

28
Q

What does kalikrein do?

A

activates bradykinin

this increases vascular permeability

29
Q

Name 3 types of late phase mast cell mediators

A

leukotrienes
prostoglandin
cytokines

30
Q

Name 6 functions of mast cell mediators

A 
vasodilation
vascular permeability
HR, contraction
grandular secretion
brochoconstriction
irritates nerve endings
31
Q

How is anaphylaxis treated?

A

intramuscular adrenaline

steroids an antihistamines to prevent late phase response

32
Q

What do allergy effector cells derive from?

A

haematopoietic stem cells in the bone marrow

33
Q

What do all allergy effector cells express?

A

FceRs

34
Q

What feature of allergy effector cells would suggest they are highly responsive?

A

they are highly granulatred

35
Q

Where would you find mast cells?

A

tissues

36
Q

What do mast cells release?

A

histamine and other immune mediators

37
Q

What do basophils release?

A

histamine

produce IL-4 and 13

38
Q

Where do basophils go?

What do they do there?

A

lymph node and prime for allergic responses

39
Q

How are eosinophils formed?

A

haematopoiesis in bone marrow stimulated by IL-5 from Th2 cells

40
Q

What do we use to stop eosinophil mediated allergic disease?

A

anti-IL5 drugs

41
Q

Name an example of eosinophil mediated allergic disease

A

severe difficult to treat asthma

42
Q

What attracts eosinophils to tissues?

A

chemokines like eotaxins

43
Q

How do eosinophil kill?

A

lysosomal granules with toxic stuff like MBP, ribonucleases, peroxides, ROS and RNS

44
Q

what is the hygiene hypothesis?

A

the lack of exposure to germs in early life skew our immune system away from Th1 towards a Th2 phenotype

45
Q

What is the evolutionary purpose of IgE-mediated responses?

A

killing parasites >D

46
Q

Why do we need a whole extra system to deal with parasites?

A

too large for phagocytes

47
Q

How do Eosinophils bind to IgE?

A

via FceR1

48
Q

how do we eradicate a dead parasite?

A

IL-13 from effector cells stimulate goblet cell hyperplasia and mucous production

GI SM contraction

3 IIH (23 decks)

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