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Immunity > 1. Hypersensitivity Reactions > Flashcards

1. Hypersensitivity Reactions Flashcards

1
Q

Define the term hypersensitivity

A

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

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2
Q

Hypersensitivity can be caused by exogenous antigens. Give 2 types of these.

A

Non-infectious substances.
Infectious microbes.
Drugs.

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3
Q

Hypersensitivity can be caused by intrinsic antigens. Give 2 types of these.

A

Infectious microbes.

Self antigens.

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4
Q

What is the sensitisation phase?

A

A persons first encounter with the antigen. Activation of antigen presenting cells and memory effector cells. Once exposed, individual is sensitised.

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5
Q

What is the effector phase?

A

A pathological reaction upon re-exposure to the same antigen and activation of the memory cells of the adaptive immunity. Is the clinical manifestation of the hypersensitivity reaction.

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6
Q

How long does a Type II hypersensitivity reaction take to develop?

A

5-12 hours

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7
Q

What antibodies are involved in a type II hypersensitivity reaction?

A

IgG or IgM.

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8
Q

What type of antigens does a Type II hypersensitivity reaction target?

A

Cell bound antigens (both exogenous and intrinsic).

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9
Q

What two types of damage can type II hypersensitivity reactions induce?

A

Tissue/cell damage or physiological change.

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10
Q

Describe the mechanism by which tissue/cell damage is causes in a Type II hypersensitivity reaction

A

Complement activation, cell lysis, opsonisation, neutrophil recruitment and activation.
Also by ab-dependent cell cytotoxicity.

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11
Q

Give one example of a type II hypersensitivity reaction caused by an exogenous antigen

A 
Haemolytic disease of the newborn (rhesus D).
Transfusion reactions (A/B antigens).
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12
Q

Give one example of a type II sensitivity reaction caused by an intrinsic antigen

A

Autoimmune haemolytic anaemia.
Immune thrombocytopenia Purpura.
Goodpasture’s syndrome.

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13
Q

A haemolytic transfusion reaction is a life-threatening condition caused by a type II sensitivity reaction involving IgM. What is the mechanism for this reaction?

A

Incompatibility in the ABO group or rhesus D antigens. So donor RBC’s are destroyed by the recipient’s immune system.

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14
Q

Haemolytic disease of the newborn is an example of a disease caused by a type II hypersensitivity reaction to IgG. What is the mechanism of this reaction?

A

Rh+ father and Rh- mother produce Rh+ foetus. In first pregnancy, antigens from developing foetus enter the moths blood during delivery and mother becomes sensitised. If the women has another pregnancy with a Rh+ foetus, her anti-Rh antibodies cross the placenta and damage feral red blood cells.

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15
Q

What is given to known Rh- mothers during pregnancy to prevent the mother becoming sensitised?

A

IgG anti-RhD - kills foetal Rh antigens.

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16
Q

By what 2 mechanisms can a type II hypersensitivity reaction cause physiological change?

A

Receptor stimulation.

Receptor blockade.

17
Q

By what mechanism is Grave’s disease a type II hypersensitivity reaction? What is the antigen?

A

Receptor stimulation increases thyroid activity. Antigen is TSH receptor.

18
Q

By what mechanism is myasthenia gravis a type II hypersensitivity reaction? What is the antigen?

A

Receptor blockade leads to impaired neuromuscular signalling. Antigen is acetylcholine receptor.

19
Q

Give one therapeutic approach to treating type II hypersensitivity reactions causing tissue damage.

A

Immune suppression to prevent complement activation.
Plasmapheresis to remove circulating antibodies and inflammatory mediators.
Splenectomy to reduce opsonisation and phagocytosis.
Intravenous immunoglobulin to cause IgG degradation.

20
Q

Give one therapeutic method of treating type II hypersensitivity reactions causing physiological change

A

Correct metabolism to reduce receptor stimulation.

Use replacement therapy to fix a receptor blockade.

21
Q

Within what time frame does a type III hypersensitivity reaction normally develop?

A

3-8 hours

22
Q

What antibodies are involved in a type III hypersensitivity reaction?

A

IgM or IgG.

23
Q

What type of antigens does a Type III hypersensitivity reaction target?

A

Soluble antigens - both foreign and endogenous.

24
Q

What type of hypersensitivity reaction causes tissue damage by immune complex deposition?

A

Type III

25
Q

Give 3 key factors affecting immune complex pathogenesis in a type III hypersensitivity reaction

A

Complex size, host response, local tissue factors.

26
Q

Give an example of a type III hypersensitivity reaction caused by a self antigen

A

Rheumatoid arthritis

27
Q

Give an example of a type III hypersensitivity reaction caused by an infection

A

Glomerulonephritis

28
Q

Give an example of a type III hypersensitivity reaction caused by the antigen being double-stranded DNA

A

Systemic lupus erythematosus

29
Q

How long does a type IV hypersensitivity reaction take to develop?

A

24-72 hours

30
Q

What cells does a type IV hypersensitivity reaction normally involve?

A

Lymphocytes and macrophages

31
Q

Contract sensitivity, tuberculin hypersensitivity and granulomatous hypersensitivity are all subtypes of what type of hypersensitivity?

A

Type IV

32
Q

What reaction is a tuberculin hypersensitivity reaction?

A

Dermal reaction

33
Q

What is the mechanism of type IV hypersensitivity?

A

In effector phase - T cells activated, producing loads of cytokines, activate macrophage, massive influx, causing tissue damage

34
Q

Give one example of a disease that is a type of granulomatous hypersensitivity (type IV).

A

TB.
Leprosy.
Schistosomiasis.
Sarcoidosis.

35
Q

Give one example of a stimulant that causes a type IV hypersensitivity reaction that is contact hypersensitivity

A

Nickel.
Poison ivy.
Organic chemicals.

36
Q

Give an example of a test in why type IV hypersensitivity is used to determine the sensitisation status of an individual

A

Mantoux test for TB

37
Q

Give an example of a type IV hypersensitivity reaction to endogenous antigens with the associated antigen.

A

Insulin-dependent diabetes mellitus, pancreatic islet cells are the antigen.
Hashimoto’s thyroidistis, thyroid gland is the antigen.
Rheumatoid arthritis, IgG antigen.

38
Q

Give 2 categories of therapy that can be used to treat type III and IV hypersensitivity reactions

A

Anti-inflammatory drugs.

Monoclonal antibodies.

39
Q

Describe the mechanism by which tissue damage is caused in a type III hypersensitivity reaction?

A

Immune complexes formed, intermediate sized immune complexes deposited in the tissue, complement activated, neutrophil chemotaxis, neutrophil adherence and degranulation, releasing enzymes and reactive oxygen species.

Immunity (5 decks)

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