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Principles of Disease > Hypersensitivity + Autoimmunity > Flashcards

Hypersensitivity + Autoimmunity Flashcards

1
Q

Define hypersensitivity

A

disorders where normally beneficial parts of an immune response act in an exaggerated or inapportppiate fashion to environmental antigens, and cause tissue damage. (bystander damage)

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2
Q

Which types of hypersensitivity are mediated by antibodies?

A

Types I, II & III

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3
Q

What causes type IV hypersensitivity?

A

Inappropriate action of Th1 cells

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4
Q

What is type 1 hypersensitivity also called?

A

allergy

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5
Q

How does Type 1 hypersensitivity arise?

A

environmental antigens (allergens) are mistake for pathogens and IgE is inappropriately synthesised

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6
Q

What does the allergen-specific IgE released during type 1 hypersensivitiy do?

A

Triggers mast cells t release inflammatory mediators like histamine and prostoglandins.

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7
Q

What are the consequences of type 1 hypersensivitiy?

A

Mucosal oedema
Capillary leakage
vasodilation
(basically inflammation)

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8
Q

what factors influence allergy problems?

A
  • genetic factors
  • hormone and neurological influences
  • environmental influences
  • immune regulatory factors
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9
Q

Why isn’t the presence of IgE alone, enough for an allergic reaction to occur?

A

A clinical allergy arises through many factors, not just immune regulatory factors so IgE can be associated with symptoms or not

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10
Q

What is it called when IgE is present but no smptoms occur?

A

Atopy

A state of sub-clinical immune sensitisation

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11
Q

What antibodies mediate Type 2 hypersensitivity?

A

IgG & IgM antibodies

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12
Q

Why is the line between type 2 hypersensitivy & autoimmune blurred?

A

Because in type 2 the IgG and IgM antibodies can bind to exogenous or self antigens

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13
Q

How does type 2 hypersensitivity occur?

A
  • IgG and IgM antibodies target antigens on the surface of cells or within tissues
  • They cause tissue damage
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14
Q

How do antibodies in type 2 cause tissue damage?

A
  • complement activation triggers cell lysis
  • Fc receptors on phagocytes bind to immunoglobulin and phagocytic activity is stimulated
  • antibody dependent cellular cytotoxicity (ADCC)
  • inhibit/stimulate cell function
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15
Q

What is immune complex formation?

A

Antigens and antibodies form complexes together. They are normally transported to the liver/spleen where they are destroyed by phagocytes

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16
Q

How does type 3 hypersensitivity occur?

A

PREDISPOSING FACTORS in the Ag or the Ab cause the immune complex to PRECIPITATE into tissues and cause inflammation

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17
Q

What are the 2 types of inflammation in type 3 hypersensitivity?

A
  • Serum sickness (immune complexes deposited throughout many tissues)
  • Arthus reaction (complexes formed locally in tissues)
18
Q

What causes type 4 hypersensitivity?

A
  • There is an environmental substance that is structurally hard to destroy or an infectious micro-organism that evades the immune system.
  • The Th1 cells OVERREACT because they’re having trouble destroying the foreign substances
19
Q

What do non-infectious environmental agents need to bind to a host protein to trigger type 4 hype?

A

Theyre generally too low of a molecular weight to produce a substantial antigenic stimulus in order to incite an immune response

20
Q

What is a hapten? (think type 4 hype)

A

The non-infectious environmental agent bound to the host protein

21
Q

What is a carrier? (think type 4 hype)

A

The host protein bound to A low mw environmental agent.

22
Q

Define an autoimmune disease

A

Clinical disorders characterised by tissue/organ damage mediated by aberrant cellular and/or humeral immunological mechanisms against autoantigens.

23
Q

Are specific autoantigens organ-specific?

A

They can be LOCALISED to certain tissues/organs or SPREAD all over the place

24
Q

Define tolerance.

A

Process where immune system avoids producing damaging reactions against self-antigens

25
Q

Define central tolerance

A

Deletion of auto-reactive T&B cells during cell maturation

26
Q

Define peripheral tolerance.

A

Inhibiting the activity of auto reactive cells that escape central tolerance

27
Q

In what cases is immune recognition of self not damaging?

A

?-T cells can recognise antigens complexes to self molecules

-Antibodies can recognise/bind to each other to regulate produciton/ctivity

28
Q

What is physiological autoimmunity?

A

Processes of self-recognition that are normal and beneficial

29
Q

What five factors make up the aetiology of autoimmune disorders?

A
  • genetic factors
  • immune regulatory factors
  • hormonal factors
  • enivornmental factors
  • “other”
30
Q

What are immune regulatory factors that help cause autoimmune disorders?

A

Defective central or peripheral tolerance mechanisms

31
Q

What “other” factors affect autoimmune disorders?

A

Age
Trauma
Malignant disease

32
Q

What is an early phase response?

A

One that occurs within minutes

Involves preformed mast cell mediators (e.g. histamine, heparin and chemotactic factors)

33
Q

What is a late phase response?

A
  • One that takes hours or days
  • It involves newly synthesised mediators like prostoglandins
  • Also involves Th2 cytokines
  • Eosinophil mediators
34
Q

What immune effector mechanisms can go wrong to cause an autoimmune disease?

A
  • Cellular (T cell) and antibody (B cell) activity
  • Autoantibody activation of complement-mediated inflammation
  • Immune complex formation (eg type 3 hypersensitivity mechanisms)
  • Recruitment of innate immune components (phagocytes/cyotkines/NK cells)
35
Q

Quick summary of the steps of an autoimmune disorder:

A
  • initiating (environmental) event [eg infection] and genetic (susceptibility) factors [eg inheritance of particular HLA alleles]
  • breakdown of self tolerance
  • autoreactivity (humeral and/or cellular)
  • tissue damage
36
Q

Do autoimmune disorders only cause damage?

A

No some cause hyper function rather than hypo (eg hyperthyroidism)

37
Q

How do overlap disorders occur?

A

OFten autoimmune disorders will often occur together if they are both very organ speciic or very not.

38
Q

What are the pathogenic mechanisms of autoimmune disease?

A
  • Immune complex formation
  • Antibody mediated
  • Cell-mediated
  • Recruitment of innate immune components (neutrophils, macrophages etc)
  • Complement system
39
Q

List some organ specific diseases:

A
  • Pernicious anaemia (stomach)
  • Adidsons disease (adrenal)
  • Hasimotos thyroiditis, - Primary Myxoedema, thyrotoxicosis (Thyroid)
40
Q

List some non-organ specific diseases:

A
  • Muscles = Dermatomyositis
  • Skin = Scleroderma
  • Kidneys = SLE
  • Joints = Rheumatoid arthritis
41
Q

Name 3 thyroid specific diseases:

A

Hashimotos thyroiditis

  • Primary Myxoedema
  • thyrotoxicotis
42
Q

What causes type IV hypersensitivity?

A

Innapropriate action of Th1 cells.

Principles of Disease (53 decks)

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