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Immunuology > Hypersensitivty > Flashcards

Hypersensitivty Flashcards

1
Q

what is hypersensitivity?

A

exaggerated inappropriate adaptive immune response

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2
Q

what is sometimes a result of hypersensitvity?

A

inflammatory reactions and tissue damage result

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3
Q

when does hypersensitivity manifest?

A

not manifest on 1st contact with Ag usually appears on subsequent contact

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4
Q

how many types of hypersensitivity are there?

A

4 -Type I, II, III and IV

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5
Q

what types are antibody mediated?

A

Types I,II, III

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6
Q

what type is mediated by T cells and macrophages?

A

Type IV

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7
Q

what immunoglobulin is involved in Type I hypersensitivity?

A

IgE

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8
Q

what is type I hypersensitivity ?

A

IgE response to innocuous environmental antigens i.e pollen, house-dust mites, latex, some drugs(local anaesthetics)

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9
Q

what does IgE bind to?

A

IgE binds to FcRI on mast cells

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10
Q

what occurs at the second encounter in type I?

A

Second encounter with allergen triggers release
of inflammatory mediators and produces acute inflammatory reaction within minutes with symptoms such as athasma and rhinitis

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11
Q

what inflammatory mediators are released in type I ?

A

Release of histamine, prostaglandins,

leukotrienes and other mediators of allergic response

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12
Q

what are 4 treatments for mild type I hypersensitivity?

A
  1. Avoidance
  2. Sodium chrooglycate
  3. anti-histamines
  4. Desensitisation
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13
Q

what is an example of a severe type I reaction?

A

anaphylactic shock

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14
Q

what are symptoms of anaphylactic shock?

A

wheeze, swelling of face
and laryngopharynx,
nausea, dizziness, fainting,
low blood pressure

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15
Q

how is anaphylactic shock treated?

A

with adrenaline immediately

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16
Q

What is type II hypersensitivity ?

A

Antibody-dependent cytotoxic hypersensitivity

17
Q

how long after exposure does type II hypersensitivity occur?

A

occurs in 12-18 hours of exposure to antigen

18
Q

when does type II hypersensitivity occur?

A

when IgG or IgM binds to either a self-antigen or a foreign antigen on cells

19
Q

what is a result of type II?

A 
Phagocytosis, killer cell activity or complement-
mediated lysis  (Damage is restricted to particular cells/tissues bearing the antigen)
20
Q

Name example of type II reactions.

A
  1. Blood transfusion reactions when ABO incompatible blood is transferred (fever, nausea,vomiting)
  2. Haemolytic disease of the newborn
21
Q

Describe the type II reaction of haemolytic disease of the newborn.

A
  • Results from incompatibility of Rhesus D blood antigens to RhD-negative mother
  • RhD-positive RBC from 1st foetus sensitise mother usually at birth
    -If subsequent foetus is RhD-positive, anti-Rh IgG produced by mother crosses the placenta and attacks foetus
  • RhD-negative mothers infused with anti-RhD IgG
    immediately after delivery - eliminates all RhD-positive RBC before immune response occurs
22
Q

what caused a reduction in child mortality from haemolytic disease?

A

Anti-RhD Prophylaxis

23
Q

when does type III hypersensitivity occur?

A

18-24 hours after exposure

24
Q

what is an example of type III?

A

extrinsic allergic alveoli’s

25
Q

what is type III hypersensitivity mediated by?

A

persistence and deposition of

antibody-antigen immune complexes

26
Q

What are immune complexes influenced by?

A
  1. Route of Ag exposure eg poor clearance in lung
  2. Dose of Ag
  3. Size of IC (larger IC fall out of circulation)
  4. Binding of Ag directly to tissues
27
Q

what happens when the immune complexes are deposited?

A

cause severe inflammation

28
Q

when does type IV hypersensitivity occur?

A

48-72 hours post Ag exposure

29
Q

what are the 3 types of type IV hypersensitivity?

A
  • contact- 48-72 hours
  • tuberculin - 48-72 hours
  • granulomatous - 21-28 days
30
Q

what is type IV hypersensitivity mediated by?

A

T cells and macrophages

31
Q

what are the two phases of type IV hypersensitivity?

A
  • sensitisation

- elicitation

32
Q

Describe sensitisation of type IV hypersensitivity.

A
  • Ag encountered by dendritic cell in skin
  • Migrates to lymph node
  • Presents Ag to CD4+ T cell
33
Q

Describe elicitation of type IV hypersensitivity.

A
  • Ag subsequently encountered
  • Memory T cells are triggered
  • Inflammation
34
Q

what dental materials is type IV hypersensitivity seen to?

A
  • Amalgam alloy
  • Gold
  • Mercury
  • Resin-based materials
35
Q

What is an example of contact type IV?

A

Eczematous reaction at point of contact with Ag i.e nickel

36
Q

what is an example of tuberculin type IV?

A

skin swelling develops after intradermal exposure i.e following injection of tuberculin bacilli

37
Q

what is an example of granulomatous type IV?

A

Granuloma formation - aggregation and

proliferation of macrophages persisting for weeks

Immunuology (10 decks)

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