03c: GI Immunology Flashcards
GI tract immune system faces specific challenges, namely from (X) pathogens.
X = food antigens and commensal bacterial (part of gut)
List general immunological structures in GI tract that battle pathogens.
- Tonsils
- Peyer’s patches
- Lamina propria follicles
T/F: GI tract immunity particularly emphasizes tight regulation, though other innate and adaptive responses present.
True
T/F: Humoral immunity plays little to no role in GI defenses.
False - major role in local defense
GI Immunity: List the two components of the epithelial barrier.
Tight junctions and mucus
List the specialized epithelial cells with immune function in GI tract.
- Adsorptive epithelial cells
- M cells
- Paneth cells
- Goblet cells
GI innate Immunity: Goblet cells important for (X) and adsorptive epithelial cells for (Y).
X = secreting mucus Y = secreting cytokines
GI innate Immunity: M cells important for (X) and paneth cells for (Y).
X = antigen sampling/presentation Y = secreting anti-bac peptides
T/F: Mucus is both a chemical and physical barrier in GI immune system.
True
Mucus: (hydrated/dehydrated) gel, made up of proteins that have been extensively modified via (X).
Hydrated
X = glycosylation
GI Immunity: Some (X) from (Y) cells stimulate mucus production in GI tract.
X = cytokines Y = epithelial
Immune system: (X) ligands, such as LPS, bind (Y) receptors. This leads to signaling events that stimulate which responses?
X = PAMPs Y = toll-like (TLRs)
Cytokines, adhesion, inflammation, adaptive immunity
T/F: Mucus contains neutrophils.
True
T/F: TLRs in GI tract are clustered together and localized to specific regions.
False - widely distributed
TLR signaling in GI tract often leads to which responses?
Increased epithelial motility, proliferation, and tight junctions (NOT inflammation)
There’s a (lower/higher) threshold for TLR activation in GI tract. Thus, (less/more) (X) needed to activate receptor.
Higher; more
X = PAMPs
Which TLR would you expect to find on luminal surface of GI tract? And on basolateral surface? What does each bind?
Luminal: TLR-4 (LPS on gram-neg bac)
Basolateral: TLR-5 (flagellin on invaded bacteria)
The (basal/luminal) surface of GI epithelium is considered “anti-inflammatory” environment, due to cell secretion of (X).
Basal;
X = IL-10 and TGF-beta
List the cells in GI tract that secrete anti-inflamm agents, specifically (X).
X = IL-10 and TGF-beta
DCs, macrophages, epithelial cells
T/F: Unlike other parts of immune system, GI tract has “anti-inflamm” DCs and macrophages that aren’t involved in antigen processing/killing.
False - they retain that function
GI Immunity: lymphocytes are (localized/scattered) throughout (mucosa/submucosa/muscularis) layer.
Scattered; submucosa
T/F: The major form of adaptive immunity in gut is humoral immunity.
True
Major form of cell-mediated immunity in GI tract comes from (X) cells.
X = Th17 and Tregs
GI Immunity: (X) cells are in contact with (basal/lateral/luminal) surface of epithelium. They act as shuttle/uber, dumping pathogen to (Y) cell.
X = M
Lateral (sandwiched between epithelial cells)
Y = DC
GI Immunity: following DC uptake, maturation, and Ag processing, MHC presentation occurs in (X).
X = mesenteric lymph nodes OR Peyer’s patches (follices/parafollicular zones)
GI Immunity: (X) species of pathogens are especially good at hijacking the (Y) cell shuttle system, thus getting past epithelial barrier no problem.
X = Salmonella Y = M
GI Immunity: (X) cells convert vitamin (Y) to (Z). This acts as a “homing signal” for which immune system cells?
X = DCs Y = A Z = retinoic acid
lymphocytes
GI Immunity: retinoic acid allows lymphocytes to home back to GI due to its (up/down)-regulation of (X).
Up-regulation;
X = CCR9 and integrin (alpha-4-beta-7)
GI Immunity: When lymphocytes home back to GI, which specific tissue layer are they returning to from circulation?
Lamina propria
The dominant protective cell-mediated immune response consists of (X) cells. Which of their actions is most prominent in GI?
X = Th17
Secretion of IL-22 (increases epithelial barrier integrity)
GI Immunity: plasma cell produces (mono/di/poly)-meric Ig(X). Of the (Y) g of Ig we make per day, how much of it is Ig(X)?
Dimeric;
X = A
Y = 3
2 of 3 g is IgA
T/F: IgA Fc segment is pro-inflammatory.
False
Invaded bacteria can actually be transported back across the epithelial cell. This is carried out by presence of (X) in (Y) tissue layer.
X = IgA Y = lamina propria
T/F: IgA levels in blood circulation are very low.
True
T/F: IgG is the only other Ab secreted in nearly same quantities as IgA in gut lumen.
False - secreted into gut lumen, but in lower quantities than IgA
GI immunity: A special receptor, (X), allows bi-directional transport of Ig(Y). Which cells express this receptor?
X = FcRn (neonatal Fc receptor)
Y = G
Intestinal epithelial cells
Major form of humoral immunity in the gut:
IgA, IgG, IgM
Crohn’s disease affects which part(s) of bowel? Which tissue layers?
Entire bowel thickness and all regions
Ulcerative colitis affects which part(s) of bowel? Which tissue layers?
Colonic mucosa
(X) disease: Unusual sensitivity to gluten proteins, manifesting as (Y) symptom in which region/tissue layers of bowel?
X = celiac Y = inflammation
Small bowel mucosa
There’s an abnormal (X) T cell response in celiac disease.
X = CD8
There’s an abnormal (X) T cell response in food allergy.
X = CD4 (Th2)
