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ESA 4 Rev > Hypersensitivity Reactions > Flashcards

Hypersensitivity Reactions Flashcards

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1
Q

What is hypersensitivity?

A

The antigen-specific immune responses that are inappropriate or excessive and result in harm to host.

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2
Q

What are the 2 types of triggers?

A

Exogenous - innocuous substances, drugs, microbes

Intrinsic - auto-immune,mimicry

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3
Q

What is a type 1 hypersensitivity reaction?

A

Allergy - Immediate reaction

Environmental - non infectious antigens

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4
Q

Which antibody is present in a type 1 reaction?

A

IgE

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5
Q

What is a type II reaction mediated by?

A

Antibody mediated

IgM - cell bound antigens

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6
Q

What is a type III reaction mediated by?

A

Immune complex mediated

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7
Q

What type of antibody is present in type III reaction?

A

IgG - soluble antigens

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8
Q

What is a type IV reaction?

A

Cell-mediated - Delayed

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9
Q

Which 3 reaction types are antibody mediated?

A

Type I,II and III

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10
Q

What are the two phases of hypersensitivity reactions?

A

Sensitization phase - first encounter with antigen. Memory cells.

Effector phase - pathological reaction upon re-exposure and activation of memory cells

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11
Q

How long does type II hypersensitivity take to develop?

A

5-12 hours

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12
Q

Give an example of an endogenous and an exogenous cause of type II reaction.

A

Exogenous - blood group antigens, rhesus D antigen.

Endogenous - self-antigens

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13
Q

What 2 types of tissue damage occur from a type 2 reaction?

A
  • Complement activation

- Antibody-dependent cell cytotoxicity

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14
Q

What are the effects of complement activation?

A

Cell lysis (MAC)
Opsonisation - C3b
Chemotaxis - C3a/5a

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15
Q

What is antibody- dependent cell cytotoxicity?

A

NK cells bind to antibody Fc receptor, release toxic radicals to kill target cells.

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16
Q

Give some examples of conditions caused by type 2 hypersensitivity.

A
  • Haemolytic disease of the newborn
  • Haemolytic transduction reaction
  • Autoimmune haemolytic anaemia
  • ITP
  • Goodpastures
17
Q

What are the physiological changes that can occur from type 2 hypersensitivity?

A
  1. Receptor stimulation - Graves’ disease

2. Receptor blockade - myasthenia gravis

18
Q

What treatment is aimed at reducing tissue damage from type 2 hypersensitivity?

A
  1. Immune suppression - complement
  2. Plasmapheresis - short term relief, allows tissue healing
  3. Splenectomy
  4. IV immunoglobin
19
Q

What is the cause of tissue damage in type 3 hypersensitivity?

A

Immune complex deposition
Complement activation
Neutrophil chemotaxis and degranulation

20
Q

How does the size of the IC affect pathogenesis of type 3 hypersensitivity?

A

Small and large easily cleared.

Intermediate less so.

21
Q

What factors affect pathogenesis of type 3?

A
  1. IC size
  2. Host response - affinity of antibody, complement deficiency
  3. Haemodynamic and physiochemical factors
22
Q

Which areas are commonly affected by IC deposition?

A

Joints
Kidney
Small vessels
Skin

23
Q

What are examples of diseases caused by type 3 hypersensitivity?

A

Rheumatoid Arthritis
Glomerulonephritis (infectious)
SLE

24
Q

What is the antigen for rheumatoid arthritis, is it present in all cases?

A

Anti-rheumatic factor

No - 75%

25
Q

What is the antigen in SLE?

A

Ds-DNA

26
Q

How long after exposure does type IV hypersensitivity occur?

A

24-72 hours -delayed

27
Q

Which cells are involved in type 4 hypersensitivity?

A

Macrophages + lymphocytes

28
Q

What are the 3 types of type IV hypersensitivity?

A

Contact hypersensitivity
Tuberculin hypersensitivity
Granulomatous hypersensitivity - if persisting antigen,most severe, tissue damage

29
Q

Give examples of granulomatous sensitivity.

A

TB
Sarcoidosis
Schistomiasis

30
Q

Give examples of contact hypersensitivity.

A

Nickel
Poison Ivy
Organic chemicals

31
Q

What is type 4 sensitivity used for?

A

Sensitization status-

Mantoux test for TB

32
Q

What diseases are caused by type 4 reactions to endogenous antigens?

A

Type 1 diabetes

Rheumatoid arthritis

33
Q

What can be used to treat type 3 + 4 hypersensitivity?

A

Anti-inflammatory - NSAIDs, corticosteroids

Monoclonal antibodies

34
Q

What is the time-scale for type 3 reactions?

A

3-8 hours

35
Q

What are poor prognostic factors of RA?

A

< 30yo
High RF titre
Female

36
Q

What is the time scale for type IV hypersensitivity reactions, why?

A

24-72 hours

Involvement of macrophages + lymphocytes

37
Q

Name 3 autoimmune diseases caused by type 4 hypersensitivity?

A

T1DM - pancreatic islet cells
Hashimoto’s
IgG RA

38
Q

Which cell mediates granulomatous type IV reactions?

A

Macrophage - later become epithelioid and giant cells.

39
Q

Give some examples of general presenting symptoms of lupus?

A 
Myalgia
Weight loss
Weakness 
Fever
Arthralgia in small joints

ESA 4 Rev (16 decks)

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