Lecture 17 Flashcards
(23 cards)
(T/F) Gut bacteria are potentially lethal if cross mucosal epithelial barrier and enter circulation
-true
What are the 4 main specialized EC in the GI tract
- goblet cells: secrete mucus
- adsorptive EC: cytokine secretion
- M cells:antigen sampling
- Paneth cells: crypt bases secreting anti-bacterial peptides
How does the GI tract limit inflammatory response of commensal bacteria?
-EC express wide range of TLRs (lower levels) but ligand stimulation increase EC proliferation and tighter junctions
TLR5 (basolateral surface) recognize which bacteria?
flagellins
What is the role of IL-10 and TGF-Beta?
anti-inflammatory cytokines
Ratio of B cells to T cells is 5x higher in which location?
Peyer’s Patches
M cells
- antigen delivery from lumen to GALT regions
- move contents via vesicles to basolateral surface for delivery to dendritic cells
Which vitamin aids in preferential homing of B cells?
-vitamin A is converted to retinoic acids by DCs to direct lymphocytes to home back to lamina propria
Intraepithlial T cells in human intestine are mostly what types of cells?
CD8+ T cells
Where are most of the CD4+ T cells found?
lamina propria as activated effector or memory T cells
Humoral immunity in gut dominated by which type of immunity?
secretory immunity by IgA and some assistance from IgG and IgM
Where does most of IgA synthesis occur?
mucosal lymphoid tissues and transported to lumen
What occurs in T-dependent isotype switching?
- DCs present processed antigen to CD4+ T cells in Peyer’s patch
- Antigen-specific T cells engage with follicular B cells, CD40-CD40L and TGFB to induce IgA class switching
- takes 5-7 days to develop response
What occurs in T-independent isotype switching?
- T cell antigens start IgA class switching by linking B cells with multiple innate immune pathways
- TLR4 ligand LPS induce class switching to IgA and mucosal B cells
How are IgA transported through EC to gut lumen (transcytosed)?
-poly-Ig receptor
What is the main purpose of secretory IgA in lumen?
-bind to microbes and prevent adherence to intestinal EC
How are IgG transported into lumen or mucosal layers?
-FcRn via re-cycling endosomal pathways
TGFB promotes expression of which T regs?
FoxP3 and inhibit generation of Th1 and Th2 CD4+ T cells
What is the function of FoxP3?
-suppress immune response and has IL-10 dominant cytokine
What are the two main types of inflammatory bowel diseases? And how to best treat them?
- Crohn’s (bowel thickness) and Ulcerative colitis (colonic mucosa)
- anti-inflammatory treatment such as anti-TNF and corticosteroids
What occurs in Celiac disease?
- atrophy of villi and malabsorption
- IgA and IgG antibodies against gluten and CD8+ T cells kill intestinal EC
- treat with gluten-free diet
What causes food allergies?
- abnormal Th2 CD4+ T cell response cause acute inflammatory response
- mediate by IgE and local mast cells (Type I HS)
Which types of cytokines stimulate peristalsis?
Th2 T cell subset
