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M&I: Overview of Immune System + Lymphocyte Development and Differentiation > Review of the Innate System > Flashcards

Review of the Innate System Flashcards

1
Q

Why do we need the inante immunity?

A

Adaptive immune response is too slow to protect us from some new pathogens

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2
Q

How long do antibodies and cytotoxic T cells take to begin to be seen in a new infection?

A
  • Antibodies start around 5 days but take longer to accumulate
  • Cytotoxic T cells start to rise on day 3/4 and peak soon
  • So a fast replicating organism could form huge numbers in the first few days if it weren’t for innate immunity
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3
Q

What is the major class of antiviral cytokines?

A

Interferon

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4
Q

What does the innate immunity recognise?

A

PAMPs

Innate immunity can not recognise specific antigens such as proteins, so it instead recognises broadly conserved pathogenic features such as structural features of a cell wall

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5
Q

What is a PAMP?

A

Pathogen Associateed Molecular Pattern

is NOT a specific antigen like what the adaptive immune response identifies, it is broad pathogenic features

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6
Q

Name some features of PAMPs

A
  • Molecules present only on pathogens and not on host cells
  • Essential for survival of pathogens
  • Invariant structures shared by entire class of pathogens
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7
Q

Name some PAMPs for gram positive bacteria

A
  • Teichoic acid
  • Lipoteichoic acids
  • peptidoglycan found in outer membrane
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8
Q

Name a PAMP for gram negative bacteria

A

Lipopolysaccharides (LPSs) found in outer membrane

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9
Q

What PAMPs can we recognise for viruses as they do not have a cell wall?

A

They do not have a cell wall but we can recognise abnormal nucleic acids (or abnormal protein glycosylation also?)

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10
Q

What is meant by how PRRs are germ-line encoded?

A

They do not change unlike in T cells or B cells that rearrange their T or B cell receptors

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11
Q

What do PRRs recognise?

A

PAMPs

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12
Q

Name the 3 functional classes of PRRs

A
  • Extracellular - recognise PAMPs outside cells
  • Intracellular/cytoplasmic - recognise PAMPs inside a cell
  • Secreted - tag circulating pathogens (like complement)
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13
Q

What is complement?

A
  • A type of PRR that is secreted
  • The complement system helps or “complements” the ability of antibodies and phagocytic cells to clear pathogens from an organism.
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14
Q

Broadly describe the purpose and effects of the inflammatory response

A
  • A generic defence mechanism whose purpose is to localize and eliminate injurious agents and to remove damaged tissue components
  • Enhanced permeability and extravasation
  • Neutrophil recruitment
  • Enhanced cell adhesion
  • Enhance clotting
  • Triggered by the release of pro-inflammatory cytokines and chemokines at the site of infection
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15
Q

Which WBCs are mostly recruited in inflammation?

A

Neutrophils

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16
Q

What are some requirements of phagocytes?

A
  • need to be able to recognise what to eat
  • need to know when they are infected

They do this by 2 SEPERATE mechanisms (they use different PRRs)

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17
Q

Name 3 professional phagocytes

A

Dendritic cells, macrophages and neutrophils

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18
Q

What are the 3 distinct roles of macrophages and dendritic cells in immunity?

A
  • phagocytosis
  • macrophages produce cytokines and chemokines to + innate and adaptive response and local inflammation
  • MHC antigeen presentation (promote or recall of an adaptive T cell response)
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19
Q

What marker do phagocytes detect on an apoptotic cell?

A

Phosphatidylserine on the exterior membrane
This is a way of detecting virus-infected cells as an infected cell will usually apoptose

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20
Q

Macrophages detect atypical sugars such as {{?}} on cell surfaces

A

mannose, fucose and beta glucan

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21
Q

What are scavenger receptors?

A

Detect non-self markers, detect various PAMPs and DAMPs

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22
Q

What are scavenger receptors?

A

Detect non-self markers, detect various PAMPs and DAMPs

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23
Q

What is macrophage passive sampling?

A

Taking in small globules of ECF and sampling it for pathogens

24
Q

{{?}} receptors are found on phagocytes to aid in the take up of complement-coated pathogens

A

Complement receptors are found on phagocytes to aid in the take up of complement-coated pathogens

25
Q

Why is it called complement?

A

Bc it complements antibodies to inactivate antigen

26
Q

Name 3 functions of complement

A
  • Opsonisation
  • Recruitment of phagocytic cells, vasoactive function
  • Punches holes in target membranes
27
Q

What are the different pathways?

A
  • Classical
  • Lectin
  • Alternative
28
Q

TLRs (toll like receptors) are expressed on {?} of phagocytes and {?}

A

TLRs (toll like receptors) are expressed on the surface of phagocytes and facing inwards on endosomes

29
Q

Do TLRs or NLRs detect viruses?

A

TLRs as they are on the endosomes so a virus after being engulfed is detected that way

30
Q

Name some targets (ligands) of TLRs

A
  • LPS
  • Lipoproteins
  • Flagellin
  • dsRNA, ssRNA (in endosomes) for viruses
31
Q

Where are NLRs found in the phagocyte?

A

NLRs are in the cytoplasm (not endosomes)

32
Q

Name some targets (ligands) of NLRs

A
  • Peptidoglycan from Gram positive and negative bacteria
  • Some viral DNA and RNA
  • Cytoplasmic PRRs
33
Q

What is the name of the receptor type of phagocytes that is predominantly for recognition of viral infection

A
  • RIG-like
  • cytoplaplasmic
34
Q

Name some targets of RIG-like receptors

A 
Viral dsRNA (we never produce dsRNA) 
- inproperly capped RNA
35
Q

Once there is binding of TLRs, NLRs or RIG-like receptors, what happens?

A

Release of specifc chemokines or cytokines from the phagocyte

36
Q

What are most cytokines (but not all) called?

A

Interleukin (then a number)

37
Q

What is the name of the main anti viral cytokine type?

A

Interferons

38
Q

What does type 3 secreted interferon do?

A

Protective of epithelial surfaces like lungs

39
Q

What does type 1 secreted interferon do?

A

Protects other surfaces like the blood and tissues

40
Q

Explain how the interferon system works

A

Infected cells with a virus release interferon which causes other cells to adopt an anti-viral state (upregulates antiviral genes)

41
Q

What pathway does IFN alpha/beta use to upregulate antiviral genes?

A

JAK/STAT

42
Q

What is the effect of interferon on protein kinase R?

A

Upregulates it

43
Q

How is protein kinase R activated?

A

viral dsRNA is a cofactor for protein kinase R so activates it

44
Q

What is the effect of protein kinase R?

A

Full translational arrest of the cell and also the viral components in the cell

45
Q

What are defensins?

A

These are short antimicrobial peptides that are secreted to kill bacteria

46
Q

How do defensins usually work?

A

Disrupting cell wall leading to lysis of bacteria

  • some are induced by bacterial infection
  • offer broad protection
47
Q

Do interferons and defensins offer specific or broad protection?

A

Broad - they are part of the innate IS
- do not bind to any sort of specific antigens, but have a general antiviral/antibacterial response

48
Q

Describe the properties of natural killer cells (what are they)

A
  • 4% white blood cells
  • Lymphocyte-like but larger with granular cytoplasm
49
Q

Describe the properties of natural killer cells (what are they)

A

Certain tumour cells and virally infected cells

50
Q

What do natural killer cells kill?

A

Certain tumour cells and virally infected cells

51
Q

How do natural killer cells kill their targets?

A

By cytotoxic molecules called granzymes and perforins - inject them in. Also by Fas

52
Q

Explain how natural killer cells know which cells to kill

A

By identifying a cell as having a ‘loss of self’
- done in multiple ways

53
Q

Fully explain the mechanism of how NK cells detect loss of self cells that they will kill

A

NK cells will recognise MHC class 1 (which is on basically all cells) which will present random antigens

  • if it detects MHC1 and an antigen then it does nothing
  • many pathogens (particularly viruses) downregulate MHC1 as it is used for antigen presentation
  • if NK cell does not bind to MHC1 then it kills the cell
54
Q

Diseases associated with inherited defects in innate immunity

A
55
Q

Describe the difference between innate and adaptive immunity in terms of cell types, speed, memory, specificity, receptors and strategy of recognition

A

M&I: Overview of Immune System + Lymphocyte Development and Differentiation (6 decks)

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