name the 4 components of the small intestine and their function
- stomach; stir and mix food with gastric juices
- duodenum
- jejunum; majority of nutrient uptake
- ileum
name the 8 components of the colon and their function
- cecum; receive food particles from ileum
- vermiform appendix; site of appendicitis
- ascending colon; water absorption
- transverse colon; water absorption
- descending colon; waste storage
- sigmoid colon; carry waste to rectum
- rectum
- anus; ejection of fecal
name the 4 immune cells found in the Peyer’s patch
M-cells, DC, B/T cells
name the 3 immune cells found in the lamina propria
macrophages, DC, mesenteric LN
what is the histological difference between small intestine and colon?
small intestine has folds and villi for surface enlargement for nutrient uptake, colon has no villi and folds and more bacteria (but ileum has more diverse bacteria)
which lymphoid tissue drains the intestinal tract?
mesenteric LN
which cells can be found in the villus and crypt?
villus; goblet cells
crypt; Paneth cells
name the 4 characteristics of the host-microbial symbiosis in the GI tract
- bacteria facilitate digestion and absorption of nutrients
- bacteria-derived signals needed for normal intestinal physiology
- commensal bacteria limit pathogen colonization
- host provides a protected and nutrient-rich environment
name the 5 functions of the epithelial barrier
- microvillar extensions
- epithelial-cell tight junctions
- secreted mucins by goblet cells
- epithelial transcytosis of IgA
- antimicrobial peptides
name the 3 functions of microbial sampling in the intestine
- antigen uptake by M-cells
- antigen uptake by APC
- passive diffusion
name the 4 differences in innate immune regulation between small intestine and colon
small intestine vs. colon;
1. presence of M cells vs. absence
2. thin mucus layer vs. thick
3. presence of Paneth cells vs. absence
4. Peyer’s patches vs. isolated lymphoid follicles
describe what happens when MUC2 is lacking
loss of colon mucus, thus more susceptible to bacterial infections and intestinal inflammation
describe what happens when Paneth cells and AMPs are lacking
increased bacterial translocation
what is the role of NF-kB signalling in the gut?
intestinal homeostasis by NF-kB signaling; maintains mucosal barrier integrity and activates innate immune cells
what happens when there is repetitive microbial interaction with the epithelium?
desensitization
name the 2 functions of epithelial cells in the GI tract
- activation (inflammatory protection against invading pathogens); epithelial signals and NF-kB signaling
- desensitization (anti-inflammatory maintenance of tissue integrity); epithelial signals and NF-kB inhibition
describe the function of macrophages in the intestine during homeostasis and inflammation
- homeostasis; monocytes recruit to the lamina propria and differentiate into anergic macrophages
- inflammation; monocytes recruit to the lamina propria and differentiate into inflammatory macrophages producing high levels of pro-inflammatory cytokines and chemokines
name the inflammatory and regulatory T cell subsets in the intestine
inflammatory; Th1/2/17
regulatory; Tr1 (IL-10) and FoxP3+ Treg
how is acquired tolerance maintained for mucosal homeostasis?
ingested soluble antigen is presented by PP and MLN-DC in mucosa draining lymphoid sites resulting in suppressive T cell response
true or false? loss of tolerance is associated with reduced numbers of FoxP3+ T cells
true, so inducible FoxP3+ Tregs are essential for differentiation of mucosally induced Treg cells in the MLN (suppressive capacity)
true or false? The lamina propria is populated by effector memory T cells
true
name the 2 requirements for mucosal tolerance
- microenvironment (soluble factors)
- antigen presenting cell (DC)
what enhances FoxP3+ iTreg differentiation in the MLN?
- CD103+ DC producing vitamin A derived retinoic acid
- TGFb production in the MLN
what determines IL-10 secreting Treg induction in colon?
bacterial colonization
