Hypersensitivity Flashcards

1
Q

Explain Hypersensitivity

A

Overreaction of the immune system.
It’s tissue damaging (immunopathologic).
There are 4 types.

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2
Q

Name the environmental allergens

A

Airborne, ingested, injected and skin contact

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3
Q

Describe Type I

A

Immediate allergic reaction.
Allergens trigger degranulation of mast cells and allergen specific IgE
Releases inflammatory mediators; histamine, prostaglandin etc.

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4
Q

Describe Type II

A

Mediated by IgG/M antibodies.

  1. Fc receptor on immunoglobulin (IgG) binds to antigen cell surface.
  2. Complement cascade - complement binds to antibodies
  3. Antibody dependent cellular cytotoxicity (ADCC) activated and antigen is lysed (ruptured)
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5
Q

Describe Type III

A

Formed immune complexes (antigen and antibody) cause disease when lodged In tissue or blood vessels, or made in excess.
-Physiological complex normal: taken to liver and spleen and antigen killed by phagocytosis
-Pathological complex causes inflammation:
Abnormal complexes avoid phagocytosis and precipitate out into tissue and attract complement and neutrophils. Release of lysosome enzymes cause tissue damage.

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6
Q

Describe Type IV

A

Cell (Th1) mediated delayed hypersensitivity
Occurs as immune system can’t destroy environmental agents.
Activation of T cells, cytokines and macrophages causes tissue destruction which may be permanent

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7
Q

Define atopy

A

Production of IgE to normal, common environmental allergens

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8
Q

What is a hapten

A

Occurs in Type IV
When non-infectious antigens (too small to produce immune response) bind to host proteins to produce antigenic stimulus to induce response and host protein is a Carrier.

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9
Q

Define autoimmune disease

A

Where the body produces antibodies that attack its own tissue, destroying it.

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10
Q

Types of immunological tolerance

A

Central Tolerance - maturing B and T cell and rendered non-reactive to self
Peripheral tolerance - After maturation of T & B cells. Inhibiting auto-reactive cells which escape the central tolerance process

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11
Q

Aetiology factors of autoimmune disease

A

Genetic factor - susceptibility to develop disease
Immune regulatory factors - defective tolerance
Hormones
Environmental - infectious and environmental agents

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12
Q

Autoimmune disease mechanism

A
  1. initiating event - infection
  2. genetic factor - susceptibility
  3. breakdown of self tolerance
  4. auto-reactivity - own antibody production and activation of complement
  5. Immune complex formation
  6. Recruitment of immune defence causing tissue damage
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13
Q

Difference between organ-specific and non-organ specific autoimmune disease

A

O-S: immune response direct against antigen in single organ

N-O S: response directed against self-antigens present in many organs and tissue causing widespread tissue damage

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14
Q

What is serum sickness?

A

In type 3 - Systemic illness where immune complexes are deposited throughout many tissues

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15
Q

What is Arthus reaction?

A

In type 3 - localised disorder where the complexes form locally in the tissue

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