3: Innate Immunity: recognition and mediators

Question 1

what is the function of a sentinel cell?

Answer 1

to recognize invading pathogens

Question 2

where are sentinel cells found?

Answer 2

present in tissues, under epithelium, along vessels and within the epithelium of mucosal surfaces

Question 3

how do sentinel cells recognize pathogens?

Answer 3

via PRRs (pattern-recognition receptors) which recognize signals from PAMPs (pathogen associated molecular patterns) and DAMPs (damage associated molecular patterns)

Question 4

PAMPs come from?

Answer 4

invading microorganisms (exogenous signals)

Question 5

DAMPs come from?

Answer 5

dead/dying host cells (endogenous signals)

Question 6

what do exogenous signals consist of?

Answer 6

molecules produced by microbial invaders (essential components of microbial invaders)

Question 7

what do endogenous signals consist of?

Answer 7

molecules released by damaged, dead, or dying host cells

Question 8

DAMPs and PAMPs are recognized by what?

Answer 8

PRRs

Question 9

where are PRRs located?

Answer 9

on sentinel cells

Question 10

recognition of pathogens by sentinel cells leads to what?

Answer 10

activation of the innate immune system

Question 11

what are examples of PAMPs

Answer 11

bacterial lipopolysaccharides (LPS)
bacterial peptidoglycans
bacterial DNA
viral nucleic acids

Question 12

what kind of kill do PAMPs elicit?

Answer 12

narrowed kill

Question 13

where is LPS found?

Answer 13

gram-negative bacteria

Question 14

where are bacterial peptidoglycans found?

Answer 14

gram-positive bacteria

Question 15

what are the molecules released by DAMPs called?

Answer 15

alarmins

Question 16

what kind of kill do DAMPs elicit?

Answer 16

broad kill

Question 17

what are examples of PRRs?

Answer 17

TLRs (toll-like receptors)
RIG-like receptors (retinoic acid inducible gene)
NLRs (nucleotide-binding oligomerization domain

Question 18

what is the most important PRR?

Answer 18

TLRs

Question 19

where are RIG and NLRs found>

Answer 19

in the cytoplasm

Question 20

where are TLRs found?

Answer 20

in the cytoplasm and cell membrane (transmembrane glycoprotein receptors)

Question 21

what is the function of TLRs in the cell membrane?

Answer 21

recognize bacteria, fungi

Question 22

what is the function of TLRs in the cytoplasm?

Answer 22

recognize viruses

Question 23

what range of TLRs do cattle and humans have?

Answer 23

TLR1 to TLR10

Question 24

what are the most important TLRs?

Answer 24

TLR2 and TLR4

Question 25

where is TLR2 found?

Answer 25

cell surface

Question 26

where is TLR4 found?

Answer 26

cell surface

Question 27

what binds to TLR2?

Answer 27

lipoproteins (gram + bacteria)

Question 28

what binds to TLR4?

Answer 28

LPS (gram - bacteria)

Question 29

what does TLR2 recognize?

Answer 29

bacteria, viruses, parasites

Question 30

what does TLR4 recognize?

Answer 30

bacteria, viruses

Question 31

what happens when a bacterial PAMP binds to a TLR?

Answer 31

binding of a bacterial PAMP to a TLR2,4 generates a signaling cascade that activates 2 transcription factors:
MAPK (mitogen-activating protein kinases)
NK-kB (nuclear factor kappa B)
these transcription factors activate transcription of genes that code for different cytokines:
IL-1(interleukin 1)
IL-6
TNK-a (tumor necrosis factor 6) which then will turn on the inflammatory response

Question 32

what happens when a viral PAMP binds to a TLR?

Answer 32

the viral PAMP will bind to TLR3,7,8,9 and results in the activation of a transcription factor:
IRF-3 (interferon regulatory factor 3)
IRF-3 then activates the genes that code for Type 1 interferons (antiviral) such as IFN-B (interferon beta)

Question 33

what are the most important sentinel cells?

Answer 33

macrophages, dendritic cells, and mast cells