Mucosal Immunity Flashcards Preview

GI/Nutrition > Mucosal Immunity > Flashcards

Flashcards in Mucosal Immunity Deck (20)
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1
Q

What are specific challenges of the GI Tract immune system?

A

Tolerance to food antigens
Tolerance to microbiota but responsive to pathogens
Enormous surface areas

2
Q

What are specific anatomic structures of the GI tract’s immune system?

A

Tonsils
Peyer’s Patches
LP Follicles

3
Q

What are M cells?
What do they do?
Where are they located?

A

Specialized cells that have epithelium which target bacteria for adhesion
Transports the bacteria to DCs
Follicle Associated Epithelium (FAE) in the Peyer’s Patches

4
Q

What is special about the histology of the Peyer’s patch?

A

All lymphocytes, physiologically inflammed

5
Q

What causes a tolerogenic DC?
What are the roles of tolerogenic DCs?

A

Retinoic acid, TSLP, TGFb causes a tolerogenic DC
Results in production of tolerogenic T-cell
Th17 and regulatory T-cells
Also they induce production of MadCAM, CCL25, and CCR9 for mucosal trafficking

6
Q

What are the 3 compounds responsible for mucosal trafficking and which cell type is each associated with?

A

CCR9 – Immune cells
CCL25 – Epithelium
MadCAM – Endothelium

7
Q
What are the two mechanisms of B cell class switching in the gut?
Describe each.
A

T-dependent

DCs in Peyer’s patch present Ag and activate naïve T cells to Th1
CD40L on Th1 cells and TGFb from DCs activate naïve B cells
Becomes a differentiated plasma cell which secretes IgA

T-independent

TLRs on DC stimulate release of TGFb, APRIL, BAFF with IL6 and Retinoic Acid
These induce class switching of B cells
8
Q

What kinda of plasma cells predominate in the gut?
What does it secrete?
What is the relative abundance of the Ig in the blood?

A

IgA secreting plasma cells in LP
2-4 grams IgA/day
Only 25% of total Ig in blood

9
Q

What are the molecules involved for T cell recognition?
What are the molecules involved for B cell recognition?

A

Recognition by T Cells

TCR – 1st signal recognize peptide antigen; CD4 and CD8 is recognition component
Co-stimulatory molecule – 2nd signal recognize co-stimulatory receptor on APC

Recognition by B cells

BCR – 1st signal is by membrane bound IgM
Costimulatory molecule – 2nd signal is complement protein or TLR

10
Q

What are the secreting steps for IgA?

A

Dimeric IgA bound at J-chain is released into LP
J-chain binds to poly-Ig receptor to enter mucosal epithelial cell
Complex is cleaved to enter lumen

11
Q

What are the 3 classes of substances which induce an immune respone?

A
  • *Immunogen** – Molecule that induces an immune response
  • *Antigen** – Molecules that bind to Ab to TCR
  • *Tolerogen** – Molecule that induces immune unresponsiveness to subsequent doses of the molecule
12
Q

What is the concept of immunologic tolerance?

A

Typically suppression of immune response due to self antigen

13
Q

What factors determine immunogencicity?

A

Size – Large increases
Dose – Intermediate increases (High or low does not)
Route of Entry – SubQ > Intraperitoneal > IV > Intragastric
Composition – Complex increases
Adjuvant – Bacteria increases
Interaction with MHC complex – Complex increases

14
Q

How is mucosal tolerance mediated?

A

IgA – Neutralizes complex antigens from generating a full response
Th17 – Strengthens gut mucosa
T-reg – Mediates non-responsiveness

15
Q

What are the general causes of autoimmunity?

A

Genetic susceptibility
Environmental trigger
Uncontrolled immune response

16
Q

Which genes are thought to play a role in genetic susceptibility to autoimmunity?
How is MHC related?
Why?

A

Genetic susceptibility – HLA genes primarily but also non-HLA genes (Nod2, ATG16)

Mutations in MHC may contribute to autoimmune disease

Inefficient displaying of self-antigens
Poorly stimulate regulatory T cells

17
Q

What is the role of an environmental trigger in causing autoimmunity?

A

Activates self-reactive or suppressed lymphocytes

18
Q

What determines how a hypersensitivity reaction manifests?

A

Type of immune response

Nature and location of the target antigen

19
Q

What percent of people suffer from autoimmune diseases?
Which major types of hypersensitivity in gut diseases?

A

1-2% of individuals suffer from autoimmune disease
Major types of hypersensitivity in gut diseases: Type I & IV

20
Q

What treatment options are there for auto-immunity?

A

Systemic immune suppression

Non-systemic immune suppression therapies
Antibodies to TNF

Plasmapheresis and FcR inhibition