Innate Immunity

Question 1

Give an example of non-immune cell innate immunity.

Answer 1

Epithelial cells have defensin proteins that create pores in microbe cell walls

Question 2

What are the key cells of the innate system?

Answer 2

phagocytes: macrophages, neutrophils

Question 3

Compare macrophages and neutrophils.

Answer 3

macrophages
- long lived
- in circulation as monocytes, but found in tissues
neutrophils
- short lived
- most abundant

Question 4

Define opsonization

Answer 4

coating a particle with a molecule to enhance its recognition
ex: antibodies

Question 5

Describe mediator production function of phagocytes

Answer 5

once activated, they release:

• cytokines - prepare for combat
• chemokines - recruit other cells
• hydrolases
• reactive oxygen species

Question 6

What are PAMPs and DAMPs

Answer 6

PAMP = pathogen associated molecular pattern
DAMP = damage associated molecular pattern

Question 7

What are PRRs?

Answer 7

PAMP Recognition Receptor - present on macrophages and DCs to recognize conserved foreign sequences and recruit lymphocytes

• can be transmembrane or intracellular
• allows limited specificity to innate system

Question 8

Describe inflammation.

Answer 8

• results from innate
• if prolonged, destructive
• triggered by inflammatory mediators
• concurrent recruitment of repair mechanisms

Question 9

List the key events of inflammation.

Answer 9

1. vasodilation to increase blood flow
2. increase vascular permeability
3. WBCs arrive (neutrophils => macrophages => lymphocytes)

Question 10

Describe what happens when a toll-like receptor PRR is activated.

Answer 10

1. transcription factor NF-kB activated => gene transcription of antimicrobial factors specific to that PAMP
2. activation of the inflammasome protein complex
3. activation of caspase protease
4. activation of IL-1B
5. inflammatory chemokine

Question 11

Describe secreted PRRs.

Answer 11

ex: mannose based lectins released to bind to mannose on bacterial cell membranes
activates complement cascade

Question 12

Describe how complement cascade bridges the gap between adaptive and innate.

Answer 12

• enhances antibody response
• lysis of foreign cells
• clearing immune complexes and apoptotic cells

Question 13

Describe the classical pathway of complement activation.

Answer 13

1. C1 interacts with antibody or cell surface factors

=> C3 convertase => C3b

Question 14

Describe the lectin pathway of complement activation.

Answer 14

MBL binds to carbohydrates on pathogen surface

=> C3 convertase => C3b

Question 15

Describe the alternate pathway of complement activation.

Answer 15

spontaneous cleavage of C3 => C3b

regulated by properdin

Question 16

Describe the rest of the complement cascade after C3b is expressed on the pathogen.

Answer 16

• C3b binds to C3b receptors on phagocytic cells

- formation of membrane attack complex (MAC) that disrupts cell membrane and leads to lysis

Question 17

What substances are present in phagosomes to promote breakdown?

Answer 17

• H2O2

- NADPH

Question 18

Describe how DCs are critical cells for innate-adaptive interfacing.

Answer 18

• roams freely and has multiple PRRs => APC

- class I MHC = endogenous, class II MHC = exogenous

Question 19

List the 3 types of innate lymphoid cells.

Answer 19

1. NK - produce inflammatory mediators and activate DCs
2. produce IL-4 and allow DCs to mature
3. produce IL-17 and antimicrobial peptides

Question 20

Describe how NK cells bridge innate and adaptive.

Answer 20

continuously samples the environment for incorrect self expression

• limited diversity
• can directly kill