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3 Immunology > Hypersensitivity > Flashcards

Hypersensitivity Flashcards

1
Q

what is hypersensitivity?

A

exaggerated, inappropriate adaptive immune response that can result in inflammatory reactions and tissue damage.

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2
Q

what are the classifications of hypersensitivity?

A

type I
type II
type III
type IV

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3
Q

what is type I mediated by?

A

antibodies

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4
Q

when does type 1 occur?

A

immediately after exposure

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5
Q

type 1 occurs when what happens?

A

IgE response to an antigen that wouldn’t normally cause an immune response e.g. pollen, food, latex. IgE binds to high affinity FC receptor on mast cells. Second encounter triggers release of inflammatory mediators producing an acute inflammatory reaction.

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6
Q

treatment for mild type 1 cases?

A
  • Avoidance
  • Sodium chromoglycate - stabilises mast cells
  • Antihistamines
  • Desensitisation: gradually introduce small amount of the known allergen to trigger a different type pf adaptive immune response
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7
Q

what is anaphylactic shock?

A

severe type 1 reactions with systemic involvement

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8
Q

what are the symptoms of anaphylactic response?

A

Wheezing, swelling of the face and neck, nausea, dizziness, fainting, low blood pressure

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9
Q

how is anaphylactic shock treated?

A

adrenaline immediately

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10
Q

why is anaphylactic shock clinically relevant?

A

Can happen to anaesthetic and latex

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11
Q

what is type II mediated by?

A

antibodies

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12
Q

what is type II also called?

A

Antibody dependant cytotoxic hypersensitivity

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13
Q

when does type II occur?

A

12-18 hrs after exposure to antigen

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14
Q

type 2 occurs when what happens?

A

when IgG or IgM bind to either a self antigen or foreign antigen on cells. Results in phagocytosis, killer cell activity or complement-mediated lysis. Damage is restricted to particular cells/tissues bearing the antigen.

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15
Q

give an example of type II hypersensitivity

A

blood transfusions when incompatible blood is transfused

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16
Q

symptoms of type II

A

fever, hypotension, nausea, vomiting, pain in back or chest

17
Q

what is type III mediated by?

A

antibodies

18
Q

when does type III occur

A

within 18-24hrs after exposure to antigen

19
Q

give an example of type III hypersensitivity

A

extrinsic allergic alveolitis

20
Q

type III occurs when what happens?

A

when there is persistence and deposition of antibody-antigen immune complexes. Once deposited can cause severe inflammation

21
Q

type IV is mediated by what?

A

T cells and macrophages

22
Q

what are the two phases that occur during type IV hypersensitivity?

A

sensitisation phase
elicitation phase

23
Q

what happens in the sensitisation phase of type IV hypersensitivity?

A

Antigen is encountered by a dendritic cell in skin, migrates to lymph node, presents antigen to CD4+ helper T cells

24
Q

what happens in the elicitation phase of hypersensitivity?

A

Antigen subsequently encountered at a later time, memory T cells triggered and then get inflammation

25
Q

when does type IV occur?

A

within 48-72 hrs
but granulomatous take 21-28 days to develop

26
Q

what are the 3 types of type IV hypersensitivity?

A

contact
tuberculin
granulomatous

27
Q

how does contact type IV hypersensitivity present?

A

as rash at point of contact

28
Q

how does tuberculin type IV hypersensitivity present?

A

Presents as skin swelling after intradermal exposure

29
Q

how does granulomatous type IV hypersensitivity present?

A

Granuloma formation: aggregation and proliferation of macrophages that can persist for weeks

30
Q

why is type IV clinically important?

A

is seen with dental materials

31
Q

remember there can be more than one type of hypersensitivity happening at the same time

A

3 Immunology (8 decks)

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