Week 4- Hypersensitivity Flashcards

1
Q

What are antibody classes know as? How do they differ?

A

Isotypes, they have different binding capacities and engage with the immune system in different ways

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2
Q

How are T cells activated?

A

By encountering a specific antigen

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3
Q

What do effector CD4+ T cells do?

A

Activate B cells, macrophages

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4
Q

What do effector CD8+ T cells do?

A

Kill infected target cells and activate B cells

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5
Q

What is type I hypersensitivity?

A

Allergic reaction where antibodies are produced against common multivalents (antigens that have multiple sites for antibody attachment)

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6
Q

What antibodies mediate type I hypersensitivity?

A

IgE

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7
Q

Describe the pathway of a type I hypersensitivity reaction

A
  1. B cell helper follicular CD4 T cells and type 2 helper CD4 T cells produce type 2 cytokines IL3 and IL4
  2. These encourage B cells to produce antigen specific IgE
  3. IgE binds to mast cells and basophils via Fc epsilon receptor
  4. Cross linking and degranulation of basophils/mast cells results in the release of histamine
  5. Results in Th2 differentiation
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8
Q

What are the 3 phases of type I hypersensitivity reactions and what are their time frames?

A
  1. Early phase- mast cells produce small molecules (few mins)
  2. Later phase- Recruitment of neutrophils (few hrs)
  3. Third phase- recruitment of eosinophils and Th2 cells (3/4 days)
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9
Q

What happens in type II hypersensitivity reactions?

A

Destruction of cells by IgG or IgM antibodies binding to antigens on the cell surface

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10
Q

What are some examples of type II hypersensitivity reactions?

A

Haemolytic disease
Graves’ disease
Mismatched blood transfusion

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11
Q

What are the 3 methods by which antibodies can cause disease? Describe them

A
  1. Anti receptor activity
  2. Antibody dependent cell mediated cytotoxicity- when antibody antigen complexes cause lysis
  3. Activation of a complement cascade- antibody is recognized by complement components which leads to the formation of a membrane attack complex (MAC) causing cell death due to lack of integrity
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12
Q

What is type III hypersensitivity?

A

When antibody antigen complexes aren’t removed and deposited in blood vessels, causing inflammation and tissue damage

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13
Q

What is type III hypersensitivity in the blood vessels called?

A

Vascularitis

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14
Q

What is type III hypersensitivity in the kidneys called?

A

Glomerulonephritis

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15
Q

What is type III hypersensitivity in the joints called?

A

Arthritis

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16
Q

What occurs in systemic lupus erythematosus and where in the body?

A

Anywhere in the body, type III hypersensitivity reactions occur. Increases apoptosis leading to neutrophil dysregulation

17
Q

What happens in serum sickness? What type of hypersensitivity is it associated with?

A

Type III, when people are bitten by snakes they form antibodies against the venom, so when they are bitten the second time there is immediate and rapid inflammation

18
Q

What is type IV hypersensitivity?

A

It is T cell mediated, where memory T cells are produced against an antigen over several weeks and 2nd exposure drives response (takes 2/3 days)

19
Q

What is the most common example of type IV hypersensitivity?

A

Contact dermatitis (an antigen in poison ivy)