2. Questions: Intestinal Immune System

Gut associated lymphoid tissue

• Peyer`sche patches (PPs)

• cryptopatches (CPs)

• isolated lymphoid follicles (ILFs)

• 
  

-> inductive sites

• 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

1. GALT is embedded within the tissue

2. part of PP composed of epithelial cells

3. ILFs and CPs not have classical secondary lymphoid tissue organization

4. Produce most of IgA

• 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

1. Build structure & ECM

2. Maintain intestinal stem cell niche (WNT ↑, BMP ↓)

3. Support vessels

4. Drive morphogenesis

5. Sense via PRRs (pattern recognition)/TLRs (toll like), secrete cytokines/chemokines

6. Can present antigen (MHC II)

7. Altered in IBD/DSS

1. Natural

   • produced in thymus with IEL homing capacity

   • self reactive but quiescent & respond to tissue stress

2. Induced

   • induced during immune responses and differtiate to IEL upon entry into the epithelium

   • all seen foreign Antigen experienced

• cDC1 induce Th1 and cross-prime CD8 T cells

• cDC2 induce Th2 and Th17

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

True

Binds to and regulates composition of the micobiota.

Because TH2 responses cannot be regulated and mice produce abnormally high levels of IgE

• Microbiota

• continous pathogen exposure

• have to tolerate fodd