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pathology 1 > hypersensitivity > Flashcards

hypersensitivity Flashcards

1
Q

what is hypersensitivity?

A

state of altered reactivity in which the body reacts with an exaggerated immune response to a foreign agent

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2
Q

what is the difference between an allergy and an intolerance?

A

allergy causes an immune reaction, intolerances don’t

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3
Q

what does atopic mean ?

A

genetic disposition to an allergy

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4
Q

which type of hypersensitivity is an allergy?

A

type 1

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5
Q

type 1 hypersensitivity is mediated by what?

A

IgE

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6
Q

what is type 1 hypersensitivity?

A

allergic reaction provoked by reexposure to a specific type of antigen referred to as an allergen

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7
Q

which hypersensitivity is most common?

A

type 1

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8
Q

immediate hypersensitivity refers to which type?

A

type 1

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9
Q

atopy is associated with which typeof hypersensitivity?

A

type 1

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10
Q

type 1 hypersensitivity may cause what in extreme cases?

A

anaphylaxis

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11
Q

what is anaphylaxis?

A

acute serious allergic response

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12
Q

IgE is bound to 2 immune cells that allow it to cross link to antigens, what are these 2 cells?

A

mast cells and basophils

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13
Q

what is a hapten?

A

an organic molecule attached to a carrier protein which elicits an immunological reaction

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14
Q

some drugs may act as haptens, give an example of a drug and how it works?

A

penicillin - induce antibody mediated allergic reaction

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15
Q

the immune response in allergy begins with sensitisation, what happens to IgE during sensitisation?

A
  • IgE producing B cells are activated after 1st exposure to allergen
  • IgE binds to Fc receptor on mast cell or CD63 receptor on basophil
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16
Q

after sensitisation, elicitation takes place, what happens to IgE during this process?

A
  • IgE recognises allergen and next exposure binds rapidly causing immediate degranulation
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17
Q

the priming of IgE to respond to an antigen is known as?

A

sensitisation

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18
Q

the storms cause by IgE are a result of what?

A

elicitation

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19
Q

mast cell degranulation releases what?

A

histamine, proteases, antimicrobial peptides

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20
Q

what is cutaneous atopy?

A

wheal and flare

21
Q

what is urticaria?

A

itchy rash

22
Q

what is allergic rhinitis?

A

hay fever

23
Q

what is atopic dermatitis?

A

allergic eczema

24
Q

what happens during anaphylactic shock?

A

mast cells degranulate all over the body

25
Q

name 3 potentially fatal reactions that may occur as a result of anaphylactic shock and how they may cause death?

A
  • laryngeal oedema (suffocation)
  • bronchiole constriction (suffocation)
  • peripheral oedema (fluid loss from BV causing hypertension and heart attack)
26
Q

can can allergy be tested?

A
  • skin prick test (prick with suspected allergen)
  • blood test (measure IgE in response to allergen)
  • patch test (allergen added to metal discs taped to skin)
  • food challenge (in ITU setting)
27
Q

what is the treatment for allergy?

A
  • avoid allergen
  • drugs
  • immunological treatment
28
Q

what drugs are used for allergy and how do they work?

A

anti histamine - compete with histamine for receptors
hydrocortisone - block histamine synthesis
cromoglycate - stabilise mast cells, stop histamine release
epinephrine - immediate treatment for anaphylactic shock

29
Q

what immunological therapy is available for allergy treatment and how does it work?

A

hyposensitisation - repeat injection of allergen

- shift IgE to IgG

30
Q

what type of drugs are antihistamines?

A

inverse agonists - inactivate receptors

31
Q

what effect does epinephrine have on patients?

A
  • bronchodilation

- reduce inflammatory mediators

32
Q

what is type 2 hypersensitivity?

A

action of complement by IgG or IgM binding to antigenic cell, causing cell lysis

33
Q

give an example of type 2 hypersensitivity?

A

blood transfusion

34
Q

how does cell lysis occur during type 2 hypersensitivity reactions?

A
  • activation of complement and formation of membrane attack complex (MAC)
  • antibody dependant cell mediated cytotoxicity (NK cell)
35
Q

what is type 3 hypersensitivity?

A

-antibody regulated reaction against soluble antigens circulating in serum

36
Q

type 3 hypersensitive reactions result in the for formation of what?

A

antibody-antigen immune complexes that are deposited in organs

37
Q

what effect do antibody-antigen immune complexes produced during type 3 hypersensitivity reactions have?

A
  • activate complement
  • induce neutrophil recruitment
  • cause inflammatory damage
38
Q

give 3 examples of conditions associated with type 3 hypersensitivity reaction?

A
  • arthus reaction
  • serum sickness
  • oral erythma multiforme (EM)
39
Q

is arthus reaction systemic or localised?

A

localised

40
Q

is serum sickness systemic or localised?

A

systemic

41
Q

what causes oral erythema multiform?

A

deposition of immune complexes (IgM) in microvasculature of oral mucosal membrane

42
Q

what are the symptoms of oral erythema multiform?

A

crusty blistering of oral mucosa

43
Q

hypersensitivity to injection causes which type of hypersensitivity response?

A

type 3

44
Q

which immune cell mediates type 4 hypersensitivity?

A

T cells (CD4 and CD8)

45
Q

delayed hypersensitivity refers to which type of hypersensitivity?

A

type 4

46
Q

why us type 4 hypersensitivity referred to as delayed hypersensitivity?

A

takes time to recruit T cells

47
Q

how is type 4 hypersensitivity tested?

A

patch test on back

48
Q

type 4 hypersensitivity has a role in which systemic diseases?

A
  • crohns
  • TB
  • sarcoidosis

pathology 1 (13 decks)

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