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GIGU > Gut Immunology > Flashcards

Gut Immunology Flashcards

1
Q

What are the components of GALT?

A

Isolated lymphoid follices (ILFs)

Peyer’s Patches (PPs)

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2
Q

How do PPs and ILFs contribute to the gut immune system?

A

They lack afferent lympathic vessels so they recieve Ags from DC

Ag-loaded DCs induce differentation of T cells and T cell depedent B-cell maturation

B cells then induce the development of IgA-producing plasma cells

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3
Q

What do paneth cells and epithelial cells produce?

A

Defensins

IgA is secreted on the surface

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4
Q

How does the IgA maintain a peacful bacteria-host interaction?

A

IGa does not ativate complement

IgA does not activate phagocytes

IgA is resistant to proteolysis by peptidases

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5
Q

How do defensins interact with the inner mucous layer?

A

They have a positively charged AA side chain and a hydrophobic AA side chain

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6
Q

How is commensal bacteria regulated?

A

DC cannot penetrate the systemic circulation

B and T cells leave the mesenteric LNs through the efferent lymph, enter the bloodstream at the thoracic duct and home back to the intestinal mucosa

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7
Q

What is the role of Treg cells in the GI?

A

Treg cells suppress Th1, Th2, and Th17 responses

Treg produce IL-10 to suppress TH cells

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8
Q

How does diet affect gut microbiota?

A

Undernutrition leads to a decreased immune function

This leads to an infection with enteropathogens

Leads to impaired absoprtion

This goes back to malnutrition

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9
Q

What do SCFAs do?

A

They help induce IL-10, induce Tregs, and promote Treg function in order to support an effective IgA mediated response to gut pathogens

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10
Q

How do T-cells contribute to peripheral tolerance?

A

Some T-cells with high affinity for self-Ags will express the transcription factor Foxp3 and become natural T regulatory cells

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11
Q

What is the mechanism of oral tolerance?

A

1) Macrophages take up Ags
2) Macrophages transfer Ags to DCs in the LP
3) Ag-loaded DCs move from LP to mLNs
4) DCs stimulate naive CD4+ T cells to induced CD4_ CD25+ Foxp3+ Treg cells

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12
Q

What do DCs release in order to differentiate CD4+ T cells?

A

Retinoic acid (RA)-directly induces Treg cell differentiation

TGF-B-mediates Foxp3 upregulation in Treg cell differentiation

Indoleamine 2,3-dioxygenase (IDO)-exerts important immunosuppressive functions and induces profliferation of Treg cells

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13
Q

What is the difference between non-immune mediated ARs and immune-mediated ARs?

A

Non-immune mediated means that you lack an enzyme needed to fully digest a food (ex. Lactose interolerance)

Immune-mediated means that there is a specific immune response upon exposure to a given food (ex. Celiac’s disease)

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14
Q

What is a type I hypersensitivity to food?

A

Development of IgE against food allergens

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15
Q

What is a type II and Type IV hypersensitivity reaction to food Ags?

A

Involves activation of macrophages by allergen-Ab complexes in FcyR-dependent manner and activation allergen-specific T cells

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16
Q

Describe a primary allergen encounter

A

1) Ingested Allergen
2) TH2 response
3) Adaptive immune response by B cells that mature into plasma cells to make IgE to allergen
4) IL-4 –> IgE
5) IgE enters circulation and is rapidly bound by FcRe (CD23) on mast cells in tissues

17
Q

Describe a subsequent exposure

A

Cross-linking causes mast cell degranulation that releases:

1) Vasoactive amines
2) Cytokines/chemokines
3) Lipids

18
Q

Repeated allergen contact activates what?

A

Allergen-specific T cells and induces IgE-depdent secondary immune response

After allergen ingestion and degradation, allergen fragments are distributed throughout the body so that an allergic response develops in other parts of the body

19
Q

What are some early allergic reaction mast cell-derived mediators?

A

Histamine

TNFalpha

Granules such as tryptase, chymase and peroxidase

20
Q

What are some late allergic reaction mast cell-derived mediators?

A

Bradykinin and PAF

IL-1,2,3,4,5,6

TNFalpha

21
Q

What does histamine do?

A

SM contraction, vascular permeability

22
Q

What does bradykinin do?

A

SM contraction, vascular permeability

23
Q

What does TNFalpha and IL-1 do?

A

Targets endothelial cells, inflammation

24
Q

What does IL-5 do?

A

Sputum eosinophils

25
Q

What are some environmental factors on allergic sensitization?

A

Vitamin D, A and folate suppress inflammatory response

High fat diet promotes inflammation

26
Q

How does a skin prick food allergy test work?

A

Used to assess type I hypersensitivity

27
Q

What is the primary tool for assessing immediate hypersensitivity reactions?

A

History

28
Q

What is the gold standard for food allergy diagnosis?

A

Oral food challenge

29
Q

Explanin Non-IgE-Mediated allergic reactions to peanuts

A

1) Peanuts can contribute to shock by producing C3a
2) C3a stimulates macrophages, basophils, and mast cells to release histamine and PAF in a C3aR dependent manner
3) PAF and histamine increase vasculary permeability and SM contraction

30
Q

Give the summary for a nut-induced anaphylaxis

A

IgE is produced (mostly)

Complement and IgG1 are produced

31
Q

What are the most important allergens in a wheat allergy?

A

alpha-amylase inhibitors, germ agglutinin, and peroxidase

32
Q

How does Food-dependent Exercise-Induced Anaphylaxis work?

A

Exercise and/or aspirin enhance absoprtion of undigested immuno-reactive allergens into the circulation

33
Q

What is a cow’s milk allergy?

A

Non-IgE: Reactions are delayed, no testing needed

IgE: Occurs Immediately, testing required

34
Q

What is the main genetic predisoping factor of CD?

A

HLA-DQ2 and DQ8

35
Q

What is the defining characteristic of CD?

A

Serum autoantibodies against tissue transgluaminase 2 (TG2)

Majority of CD patients express the HLADQ2.5

36
Q

What type of hypersensitivity is CD?

A

Type IV hypersensitivity

37
Q

What test is no longer recommended for detecting CD?

A

Anti-gliadin antibody test due to the inferior accuracy

38
Q

What is the preferred screening method?

A

tTG-IgA test

GIGU (40 decks)

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