2: Innate Immunity Flashcards
what is the point of the immune system?
to defend against pathogens
pathogens
classified in many ways
range in size
- immune system the most powerful when it comes to small things we can phagocytise
important innate immune cells
macrophages, neutrophils and dendritic cells
key aspects of innate immune cells
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
white blood cells
circulate through blood and lymph system
all white blood cells are immune cells and are on constant surveillance for infection
specialised function of DCs
take up antigens (pieces of pathogen) and bring them to lymph nodes
phagocytosis
engulfment of particular material within a membrane-bound intracellular compartment called a phagosome
uptake of the cells
neutrophils / polymorphonuclear cells (PMNs) / granulocytes
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
macs and DCs
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
2 components of inflammation
injury and infection
primary role of innate immunity?
activate acute inflammation
acute inflammation
short-term immediate inflammation
what happens within minutes to hours after initial injury/infection
benefits of acute inflammation
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
what are macs/DCs triggered/activated by?
surface/internal PAMPs
PAMPs seen as foreign since they are different from human hosts
- triggers more inflammation
PAMPs
pathogen-associated molecular patterns
molecular structures unique to microbes
what do PAMPs bind to?
toll-like receptors (TLR)
after binding, TLR sends signals starting immune responses
what has PAMPs?
viruses, gram+/gram- bacteria, fungi and protozoa
what does TLR activation do?
triggers activation of macrophages and DCs to release cytokines
cytokines
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
where are cytokines released and how do they work?
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
why does a successful immune response have to be balanced?
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
what in the human body can also be PAMPs?
viral DNA and RNA
why do we not recognise our own DNA/RNA as PAMPs?
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
