GALT and its components and to what categorie does it belong?
Gut associated lymphoid tissue
Peyer`sche patches (PPs)
cryptopatches (CPs)
isolated lymphoid follicles (ILFs)
-> inductive sites
What are the major features that disntiguish GALT from other secondary lmyphoid tissues?
PPs: T&B cell area as well the DC rich subephithelial dome which communicates with the lumen via microfold cells
ILFs: composed mostly of B cells some T cells, lymphoid tissue inducer and distinct ring of DCs
CPs: mostly LTi cells
GALT is embedded within the tissue
part of PP composed of epithelial cells
ILFs and CPs not have classical secondary lymphoid tissue organization
Produce most of IgA
What are the different subtypes of epihelial cells that line the intestinal mucosa and what functions do these subsets have in helping maintain barrier function?
Enteroytes: form barrier & help transcport IgA
Goblet cells: produce mucous important for expulsion of pathogens
Tuft cells: sense pathogens and secrete cytokines that can allert the immune system
Paneth cells:
help sustain stem cells that renew the gut produce AMPs and from thight junctions
express PRRs
produces cytokines
Why are lamina propria(bestimte schicht) stromal cells immunologically relevant?
Build structure & ECM
Maintain intestinal stem cell niche (WNT ↑, BMP ↓)
Support vessels
Drive morphogenesis
Sense via PRRs (pattern recognition)/TLRs (toll like), secrete cytokines/chemokines
Can present antigen (MHC II)
Altered in IBD/DSS
What are the key differences between the types of IELs and what are their key functions?
Natural
produced in thymus with IEL homing capacity
self reactive but quiescent & respond to tissue stress
Induced
induced during immune responses and differtiate to IEL upon entry into the epithelium
all seen foreign Antigen experienced
There are two major subsets of dendritic cells, cDC1 and cDC2. What are the key differences between them in terms of their ability to induce T cell respones in the mLN?
cDC1 induce Th1 and cross-prime CD8 T cells
cDC2 induce Th2 and Th17
How do T cells primed in the mLN know where to go once in the circulation?
DCs in the mLN imprint them during priming with gut homin molecules specific to the gut
These are CCR9 and a4b7, whose ligands CCL25 and MadCAM-1 are expressed by the gut epithelium
IgA is critical for intestinal homeostasis and infection. In what way is this statement true or false?
True
Binds to and regulates composition of the micobiota.
Mice that do not have microbiota are more susceptible to allergic responses. Why is that?
Because TH2 responses cannot be regulated and mice produce abnormally high levels of IgE
What are the biggest challenges that the gut immune system has to face?
Microbiota
continous pathogen exposure
have to tolerate fodd
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