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BOD > Immune Response to Pathogens > Flashcards

Immune Response to Pathogens Flashcards

1
Q

Give four components of the immediate defence

A
  1. Complement
  2. Antibodies
  3. Phagocytic cells
  4. Antimicrobial peptides
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2
Q

How fast does the immediate defence act?

A

0-4 hours

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3
Q

What pathway of complement opsonises pathogens for phagocytosis?

A

Alternative mainly

Also maybe lectin

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4
Q

When can the classical pathway be used?

A

If natural or specific antibody is present

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5
Q

Where is the membrane attack complex used?

A

Directly destroying Gram-negative bacteria

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6
Q

What genetic defects in complement predispose to immune complex disease?

A 
C1q
C1r
C1s
C2
C4
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7
Q

What genetic defects in complement predispose to recurrent pyogenic infections?

A

C3
Factor H
Factor I

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8
Q

What genetic defects in complement predispose to Neisseria infections?

A 
C5
C6
C7
C8
Properdin
Factor D
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9
Q

How do macrophages and neutrophils recognise pathogens?

A

Complement, scavenger and other receptors

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10
Q

What infection is associated with leukocyte adhesion deficiency (LAD)?

A
  1. Staphylococcus species
  2. Enteric gram-negative bacteria
  3. Fungal infections, esp. C. albicans
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11
Q

What is natural antibody?

A

IgM

Made without previous exposure to antigens

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12
Q

What produces natural antibody?

A

B-1 cells

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13
Q

What are defensins?

A

Major group of human antimicrobial peptides

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14
Q

What do defensins do?

A

Disrupt cell membranes

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15
Q

What are defensins effective against?

A
  1. Gram-negative and Gram-positive bacteria
  2. Fungi
  3. Parasites
  4. Enveloped viruses
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16
Q

What produces defensins?

A

Epithelial cells in skin, respiratory and urogenital tracts

Paneth cells in small intestine

Neutrophils

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17
Q

Where are β-defensins produced?

A

Urogenital tract

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18
Q

Where are α-defensins produced?

A

Paneth cells in small intestine

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19
Q

How fast does the induced innate response act?

A

4 hours to 4 days

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20
Q

What is the main component of the induced innate response?

A

Macrophages

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21
Q

What do macrophages do in the induced innate response?

A

Activated PRRs signal production of pro-inflammatory cytokines

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22
Q

What are the pro-inflammatory cytokines?

A
  1. IL-1
  2. IL-6
  3. IL-12
  4. TNF-α
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23
Q

What are the six functions of TNF-α?

A
  1. Induces adhesion molecule expression on vascular endothelium
  2. Increases vascular permeability
  3. Triggers platelet activation and blood clotting
  4. Stimulates dendritic cell activation and migration to lymph nodes
  5. Stimulates acute phase response
  6. Primes newly recruited neutrophils
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24
Q

What is the result of increased vascular permeability?

A
  1. Neutrophil migration

2. Inflammatory exudate

25
Q

What pathogens do interferons deal with?

A

Viruses

26
Q

What is the role of RIG-1-like receptors?

A
  1. Detect presence of viral nucleic acid in cytoplasm of infected cells
  2. Induce expression of type 1 interferons
27
Q

What are the type 1 interferons?

A

IFNα and IFNβ

28
Q

What is the effect of type 1 interferons?

A
  1. Induce antiviral state in surrounding cells by interfering with viral replication
  2. Activate natural killer cells
29
Q

What is the role of IFNγ?

A

Macrophage activation

30
Q

What proportion of lymphocytes do NK cells make?

A

5-25%

31
Q

What is the role of NK cells?

A
  1. Kill infected host cells

2. Secrete cytokines that act on macrophages to upregulate phagocytosis and inflammatory cytokine production

32
Q

Which cytokines recruit NK cells to sites of infection?

A
  1. IFNα and IFNβ

2. IL-12

33
Q

What is the relationship between macrophages and NK cells?

A

Activate each other

34
Q

What is the effect of NK cells on dendritic cells?

A

Signals need for initiation of adaptive immunity

35
Q

How fast is the adaptive response?

A

4 days onwards

36
Q

What four things does the adaptive response require?

A
  1. Dendritic cell activation and migration to secondary lymphoid organs
  2. Activation of low frequency T cells
  3. Activation and proliferation of antigen-specific B cells by activated T cells
  4. B cell differentiation into plasma cells for antibody production, B cell isotype switching and affinity maturation
37
Q

What do CTLs kill?

A

Cells harbouring intracellular viruses and parasites

MHC class I restricted

38
Q

What is the role of TH1 cells?

A

Activate macrophages via IFNγ

39
Q

What is the role of TH2 cells?

A
  1. Direct IgE production
  2. Help eosinophils, basophils, mast cells and B cells resist parasite infections

via IL-4

40
Q

What is the role of TH17 cells?

A

Help neutrophils respond to extracellular bacterial and fungal infections

Via IL-17

41
Q

When does specific antibody appear?

A

5 days post infection

42
Q

What is the first antibody isotype to be produced?

A

Specific IgM

43
Q

What does IgM do?

A
  1. Recruits complement

2. Compensates for low affinity with high avidity

44
Q

What does IgE do?

A

Eosinophil recruitment

45
Q

What does IgG do?

A

Neutralisation

46
Q

What does IgG1 do?

A

Opsonisation

47
Q

What does IgA do?

A
  1. Neutralisation

2. Epithelial transport

48
Q

What are the principle innate mechanisms against extracellular bacteria?

A
  1. Complement activation
  2. Phagocytosis
  3. Acute inflammatory response
49
Q

What is the principle adaptive mechanism against extracellular bacteria?

A

Specific antibody

50
Q

What is the role of secretory IgA?

A

Block binding to epithelial cells

51
Q

What three roles do the CD4+ helper T cells assist with?

A
  1. TH17 cells stimulating neutrophil recruitment
  2. TH1 cells activating macrophages
  3. Helper T cells required for thymus-dependent antibody production
52
Q

What type of T cell response do helminths induce?

A

TH2

53
Q

What does the TH2 response involve?

A
  1. IgE
  2. IgG1
  3. IgG4
  4. Eosinophils
  5. Expansion of basophils, mast cells and alternatively activated macrophages
54
Q

What do natural killer cells do?

A
  1. Kill virally infected cells

2. Secrete inflammatory cytokines

55
Q

What does the cell-mediated response to viruses mainly rely on?

A
  1. Cytotoxic T cells

2. Helper TH1 cells

56
Q

How is protective immunity to viruses established?

A

Neutralising antibody produced following vaccination or natural infection

57
Q

What do CD4-TH1 cells express to activate macrophages?

A

CD40L

58
Q

How does Leishmania prevent MAC formation?

A

Uses a surface protease (gp63) to cleave C3b to iC3b

However this increases macrophage uptake as iC3b is an opsonin

59
Q

What is the main innate response to protozoa?

A

Phagocytosis

BOD (8 decks)

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