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Immunology > Delayed hypersensitivity > Flashcards

Delayed hypersensitivity Flashcards

1
Q

What is Type II hypersensitivity?

A

A hypersensitivity reaction mediated by IgG or IgM antibodies that target antigens on cell surfaces or extracellular matrix

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2
Q

What mechanisms cause tissue damage in Type II hypersensitivity?

A

Complement activation opsonization antibody-dependent cellular cytotoxicity (ADCC) and inflammation

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3
Q

What are common examples of Type II hypersensitivity reactions?

A

Hemolytic anemia Goodpasture syndrome and rheumatic fever

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4
Q

What happens in hemolytic anemia caused by Type II hypersensitivity?

A

Antibodies target red blood cell surface antigens leading to their destruction by complement or phagocytosis

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5
Q

What is the mechanism of Goodpasture syndrome?

A

Antibodies bind to basement membrane antigens in the lungs and kidneys causing inflammation and tissue damage

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6
Q

What is antibody-dependent cellular cytotoxicity (ADCC) in Type II hypersensitivity?

A

Antibodies bind to cells recruiting NK cells to kill the target cell via perforin and granzymes

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7
Q

How does rheumatic fever involve Type II hypersensitivity?

A

Antibodies against streptococcal antigens cross-react with heart tissue causing inflammation and damage

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8
Q

What treatments are used for Type II hypersensitivity?

A

Corticosteroids plasmapheresis to remove antibodies and immunosuppressive drugs

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9
Q

What is Type III hypersensitivity?

A

A hypersensitivity reaction caused by immune complexes formed between antigens and antibodies that deposit in tissues

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10
Q

What are immune complexes?

A

Aggregates of antigens and antibodies that can activate complement and recruit inflammatory cells

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11
Q

What happens when immune complexes deposit in tissues?

A

They trigger inflammation complement activation and tissue damage

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12
Q

What are common examples of Type III hypersensitivity reactions?

A

Systemic lupus erythematosus (SLE) post-streptococcal glomerulonephritis and serum sickness

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13
Q

What is the mechanism of SLE in Type III hypersensitivity?

A

Autoantibodies form immune complexes with nuclear antigens which deposit in tissues and cause inflammation

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14
Q

What happens in post-streptococcal glomerulonephritis?

A

Immune complexes formed after a streptococcal infection deposit in the kidney glomeruli causing inflammation

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15
Q

What is serum sickness?

A

A reaction to foreign proteins in antiserum causing immune complex deposition and systemic symptoms like fever and rash

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16
Q

What is the Arthus reaction?

A

A localized Type III hypersensitivity reaction caused by immune complex deposition at the site of antigen injection

17
Q

How does complement contribute to Type III hypersensitivity?

A

Complement activation by immune complexes leads to inflammation vascular permeability and recruitment of neutrophils

18
Q

What is the role of neutrophils in Type III hypersensitivity?

A

Neutrophils are attracted by immune complexes and release enzymes and reactive oxygen species causing tissue damage

19
Q

What treatments are used for Type III hypersensitivity?

A

Corticosteroids immunosuppressive drugs and plasmapheresis to remove circulating immune complexes

20
Q

What is Type IV hypersensitivity?

A

A cell-mediated hypersensitivity reaction involving T cells and cytokines occurring 24 to 72 hours after antigen exposure

21
Q

What cells mediate Type IV hypersensitivity?

A

TH1 cells CD8+ T cells and macrophages

22
Q

What are common examples of Type IV hypersensitivity reactions?

A

Contact dermatitis tuberculin skin tests and graft-versus-host disease

23
Q

What cytokines are involved in Type IV hypersensitivity?

A

IFN-gamma TNF-alpha and IL-12

24
Q

What is the mechanism of Type IV hypersensitivity?

A

Antigen-presenting cells activate TH1 cells which release cytokines to recruit and activate macrophages and CD8+ T cells

25
Q

What happens during the sensitization phase of Type IV hypersensitivity?

A

T cells are primed by antigen-presenting cells and develop antigen specificity

26
Q

What happens during the elicitation phase of Type IV hypersensitivity?

A

Antigen re-exposure activates memory T cells leading to cytokine release and tissue damage

27
Q

What are common causes of contact dermatitis in Type IV hypersensitivity?

A

Allergens like nickel poison ivy and latex

28
Q

How does the tuberculin skin test involve Type IV hypersensitivity?

A

It measures immune memory to Mycobacterium tuberculosis antigens by inducing a delayed inflammatory response

29
Q

What is graft-versus-host disease (GVHD) in Type IV hypersensitivity?

A

Donor T cells attack recipient tissues after transplantation causing a delayed inflammatory response

30
Q

What treatments are used for Type IV hypersensitivity reactions?

A

Corticosteroids immunosuppressive drugs and antihistamines to control inflammation

31
Q

How does Type IV hypersensitivity differ from Types I II and III?

A

Type IV is mediated by T cells and does not involve antibodies whereas Types I II and III involve antibody-mediated mechanisms

Immunology (25 decks)

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