Innate immunity 3 Flashcards
(26 cards)
dendritic cells
- main function
communication with adaptive immunity
presentation of antigens
NOT directly attack invading microbes
dendritic cells
- where do they reside?
- what do they do here?
- how do they migrate?
- what do mature DCs do?
peripheral tissues
take up pathogens + their antigens
via lymphatic vessels to regional lymph nodes
activate naive T cells in lymphoid organs e.g. lymph nodes
- as DCs display antigens
lymphatic system
- made up of?
- what do lymph nodes do?
lymphoid immune tissues/organs
trap interstitial fluids draining from tissues
lymphatic system
- how does interstitial fluid travel through the system,?
system of ducts traveling from blood vessels via veins
- > creates pressure (due to valves)
- > moves slowly through tissues
lymph node
- structure
- contain what cell type?
- what happens here?
small, kidney shaped
1.2cm long
lymphocytes
macrophages
other immune cells
exchange between innate and adaptive systems
- DCs displaying antigens interact with other immune cells
dendritic cells
- what happens on infection?
DCs recognise pathogens via PRRs + MAMPs
-> take up pathogens via phagocytosis
take up viruses + extracellular material via macropinocytosis
DCs travel to lymph nodes
-> display antigens to adaptive immune cells
what is the basic function of the lymph nodes?
used to sample infection
- higher conc of DCs = bigger infection
antigen presentation
- APCs
- how are the antigens derived?
- how are the peptide antigens loaded onto the surface?
= antigen presenting cells
- macrophages + DCs
from destruction of pathogens in phagolysosome
loaded onto MHC
- major histone compatability complex
antigen presentation
- 2 types of MHC
MHC 1
= all nucleated cells
- endogenous antigens
(generated inside cell)
MHC 2
= on APCs
- exogenous antigens
(sampled from outside cell)
CD8 T cell
CD4 T cell
deals with virus-infected host cells - CD8 on target cell binds the alpha3 domain of MHC class 1
deals with extracellular pathogens - CD4 on APC binds the beta2 domain of MHC class 2
DCs in mucosal surveillance and homeostasis
DCs residing in GALT (gut associated lymphoid tissues)
- monitor luminal contents (sensing antigens)
+ ensure appropriate response
GALT
- Peyer’s patches
similar organisation to lymph nodes
sites where luminal contents continually sampled
-> antigens shown to resident immune cells
GALT
- Microfold cells (M cells)
- DCs
deliver material from gut lumen to underlying immune cells
(include resident DCs)
DCs can directly sample luminal contents
- extend dendrites between epithelial cells
intracellular pathogens
all viruses = obligate intracellular pathogens
many bacteria function as intracellular pathogens
intracellular pathogens
- barriers against
innate physical barriers help exclude viral infection
some TLRs recognise viral MAMPs
RIG-1- Like receptors detect viral nucleic acids in infected cells
RIG-1- Like receptors (RLRs)
= retinoid acid inducible gene 1
in cytoplasm
induces production of interferons
interferons
type 1
- induce production of intracellular proteins that inhibit viral replication in host cells
type 2
- activate white blood cells that deal with infected host cells
- > kills host cells
interferons
- signalling
host cell 1 infected by virus
- > makes interferon
- > BUT killed by virus
interferon enters host cell 2
- > induces changes to protect cell
e. g. antiviral proteins
TLR mediated interferon response
TLR7 and TLR3 found in endosomes
-> recognise ssRNA or dsRNA
(viral nucleic acids)
-> signalling
-> production of type 1 interferons (IFN-alpha and beta)
via cascade similar to other TLRs
+ interactions with interferon regulatory factors (IRF7 + IRF3)
interferons
- detection of viral infection
triggers phosphorylation + translocation of IRF3 to nucleus
-> activates INF-B
-> INF-B secreted out of cell
-> autocrine effect = works on infected cell
OR
paracrine effect = works on nearby cells
- > stimulates production of other INF types + induce interferon response inhibitory to viral replication
(e. g. increasing MHC 1 expression so viral antigens are presented)
3 interferon responses
induce resistance to viral replication in all cells
increase expression of ligands for receptors on NK cells
activate NK cells to kill virus-infected cells
natural killer (NK) cells - 2 main functions
kill infected host cells (self cells)
increase/maintain inflammation
NK receptors
NK cells have cell-surface receptors that activate/inhibit cell killing
- use a combination of both to evaluate host cells
NK recognition of healthy cells
healthy cells express range of surface features that act as ‘don’t kill me’ signals to NK cells
