2: Innate Immunity

Question 1

what is the point of the immune system?

Answer 1

to defend against pathogens

Question 2

pathogens

Answer 2

classified in many ways

range in size
- immune system the most powerful when it comes to small things we can phagocytise

Question 3

important innate immune cells

Answer 3

macrophages, neutrophils and dendritic cells

Question 4

key aspects of innate immune cells

Answer 4

phagocytic and can kill bacteria/pathogens by engulfing them
- especially neutrophils

release mediators which directly kill pathogens

produce cytokines to trigger inflammation and attack other cells

• cytokines as molecules that control immune response
• tell the rest of the immune system what to do

macs and DCs have a key role in activating adaptive immunity

Question 5

white blood cells

Answer 5

circulate through blood and lymph system

all white blood cells are immune cells and are on constant surveillance for infection

Question 6

specialised function of DCs

Answer 6

take up antigens (pieces of pathogen) and bring them to lymph nodes

Question 7

phagocytosis

Answer 7

engulfment of particular material within a membrane-bound intracellular compartment called a phagosome

uptake of the cells

Question 8

neutrophils / polymorphonuclear cells (PMNs) / granulocytes

Answer 8

most abundant white blood cells

has a nucleus so a lot more constant DNA transcription and RNA translation

loaded with granules containing toxic proteins and enzymes killing bacteria
- macs and DCs also kill bacteria if activated by cytokines

can cause a lot of tissue damage so dangerous

short-lived but replenished quickly from bone marrow

Question 9

macs and DCs

Answer 9

found virtually in every tissue

clean up dead cells, activate adaptive immunity

secrete cytokines, proteases and nucleases to orchestrate inflammation

detect pathogen with special pathogen sensor proteins
- acting as sentinels

Question 10

2 components of inflammation

Answer 10

injury and infection

Question 11

primary role of innate immunity?

Answer 11

activate acute inflammation

Question 12

acute inflammation

Answer 12

short-term immediate inflammation

what happens within minutes to hours after initial injury/infection

Question 13

benefits of acute inflammation

Answer 13

inflammation brings innate immune cells to an infection site for phagocytosis

• kill bacteria and repair tissues
• not always able to kill all of it

fluid cleanses site of infection
- inflammation brings fluid to flush out pathogens

immune molecules like antibodies brought to the site of infection

signalling to activate adaptive immune system
- bacteria replicating and there’s infection

inflammation can also cause damage to uninfected cells

Question 14

what are macs/DCs triggered/activated by?

Answer 14

surface/internal PAMPs

PAMPs seen as foreign since they are different from human hosts
- triggers more inflammation

Question 15

PAMPs

Answer 15

pathogen-associated molecular patterns

molecular structures unique to microbes

Question 16

what do PAMPs bind to?

Answer 16

toll-like receptors (TLR)

after binding, TLR sends signals starting immune responses

Question 17

what has PAMPs?

Answer 17

viruses, gram+/gram- bacteria, fungi and protozoa

Question 18

what does TLR activation do?

Answer 18

triggers activation of macrophages and DCs to release cytokines

Question 19

cytokines

Answer 19

secreted proteins considered as immune hormones since they are made by a cell and used on another

how the immune system interacts and communicates between cells

alert signals for inflammation

not unique to immune system

Question 20

where are cytokines released and how do they work?

Answer 20

proteins released at the site of infection and work close by primarily but can travel through blood

bind to receptors on other blood cells, transmit signals to increase both innate and adaptive immune response

Question 21

why does a successful immune response have to be balanced?

Answer 21

too much cytokine means too many immune cells are activated - ‘shock’ or death

too little cytokine means too little immune cells are activated - failure to contain infection

Question 22

what in the human body can also be PAMPs?

Answer 22

viral DNA and RNA

Question 23

why do we not recognise our own DNA/RNA as PAMPs?

Answer 23

PAMPs recognised outside or inside macs based on where they are

when DNA/RNA is recognised as a PAMP, usually it’s found in a place/form distinct from normal place/form
- DNA/RNA very controlled

location very relevant as to whether something becomes a PAMP or not

viruses typically replicate in cytoplasm so if it’s detected there it’s a PAMP
- host cell DNA is normally only in the nucleus