Microbiome and barrier immunity Flashcards
List 5 barriers that separate the outside from the inside
- oral epithelium
- skin epithelium
- airway epithelium
- intestinal epithelium
- cervical epitherlium
What is barrier immunity?
immune system associated with skin and mucosal tissues
How is homeostasis maintained in barrier immunity?
by a combination of mechanisms that inhibit inflammation and promote tolerance
What is the commensal microbiome?
the diverse community of microbes (bacteria, viruses, fungi and worms) that coexist with our barrier tissues without causing damage; commensal microbes provide diverse benefits to barrier tissues
Why are commensal bacteria important?
- breakdown indigestible complex plant polysaccharides
- generate essential vitamins
- protects from pathogenic bacteria by taking up space
- establish regulatory environment of the gut
- proper development of the immune system
What are commensal bacteria affected by?
- diet: probiotics and prebiotics
- antibiotics
- stress
How do epithelial cells act in barrier immunity?
- provide a physical barrier
- protective mucus layer
- secrete AMPs that kill or inhibit bacteria
- beating cilia that sweep pathogens away
What is the role of the GIT in barrier immunity?
- maintain the well-being of commensal microbiome
- regulate local and systemic immune responses
How is Ag delivered to APCs in the GIT?
- M cell R’s: transcytose Ag and microbes but also carry IgA-Ag complexes from lumen to lamina propria
- goblet cells: convery small soluble Ag from lumen to lamina propria
- resident APCs: extend processes between epithelial cells and sample Ag from lumen
What kind of immune response does barrier immunity initiate? What are the characteristics of a healthy vs damaged barrier?
barrier immunity initiate tolergenic and inflammatory responses to microorganisms
healthy = homeostatic balance –> tolergenic
damage = damaged epithelial cells send specific signals to immune cells that initiate an inflammatory immune response
Describe the tolergenic responses of barrier immunity
- cell-cell and cell-microbe interactions trigger production of anti-inflammatory molecules and cytokines
- epithelial cells help maintain barrier by secreting AMPs and TGF-beta
- TGF-beta and IL-10 enhance production of Tregs and IgA secreting B cells
- Tregs produce anti-inflammatory cytokines and control immune cell activation
- IgA bind to commensal microbes, preventing them from penetrating the epithelial barrier and initiating an inflammatory immune response
Describe how IgA is secreted into the lumen of the intestine
- epitherlial cells are polarized
- apical side contacts lumen and exports IgA
- basolateral side surface polymeric Ig Rs capture and internalize IgA made in lamina propria
What are some functions of IL-22 on epithelial cells?
- regulate epithelial cell growth
- promotes mucus secretion/production
- promote AMP production
- promote tight junctions
What is gut dysbiosis?
disruption of a healthy microbiome
Name and describe two diseases that cause gut dysbiosis
- IBD
- chron’s –> innapropriate type 1
- ulcerative colitis –> innapropriate type 2 - celiac
- autoimmune disorder triggered by gluten
- production of IL-5 activated IEL = epithelial cell death
- triggers Th1 response and NK and B cell activity
