6 Gut Immunity, Nutrition, and Adverse Food Reactions Flashcards
What antibody is mainly used in the gut
IgA
It resists proteolysis in the GI
Defects in the epithelial barrier can result in what
Allergen sensitization
What is the main cell type responsible for oral tolerance
Treg and TGFβ
What cytokine functions to suppress the immune system
IL10
What does TGFβ do in the gut
Facilitates class switching from IgM to IgA
Th1 heavy reactions in the gut lead to
Inflammation and Crohns
Th2 heavy reactions lead to q
Allergies and adverse food reactions
What role does retinoic acid play in oral tolerance
Helps form the dendritic cells which are responsible for sampling
What does IDO do
Helps induce Treg
Where are Ags captured
Lamina propria and peyers patches
DCs stimulate Treg through what signals
TGFβ, retinoic acid, and IDO
What do macrophages express to expand Tregs
IL10
What molecules suppress inflammation
Vitamin D, A, and folate
How does the microbiota suppress allergic reactions
Inducing Tregs
What ab is involved in allergies
IgE
What cell type does the microbiota suppress
Basophils and mast cells
What other T cell type do Tregs downregulated
Th2 which is essential for generating IgE
What nutritional factors promote the development of allergies
High fat diet and MCT
What nutritional factors suppress allergies
Vitamin D, A, and LCT
How does the gut microbiota function to suppress allergy
Decreasing IgE
Increasing Tregs
What factors can help create a good symbiotic relationship for gut bacteria
Short chain FA
Polysaccharide A
Peptidoglycan
What factors can disrupt the gut microbiota
Malnutrition
Decreased immune function
Impaired absorption
Infections
What are the types of food reactions
Immune mediated (food allergy and celiac dx)
Nonimmune mediated (food intolerances)(lactose)
IgE mediated reactions are Type __ hypersensitivity and non-IgE mediated reaction are Type ____ and ______
1; 3; 4
IgE mediated reactions have what phases
Immediate (mast cells)
Late-phase
What are non-IgE mediated reactions believed to be caused by
T cells typically 4-28 hours
Food allergies can have reactions in what systems
Skin, gastrointestinal, and respiratory
The most common food allergy is what
Milk
Within the first 3 to 5 years what allergies are normally lost
Milk, eggs, wheat, soy
What allergies are likely to continue into adulthood
Peanuts, tree nuts, fish, shellfish
What induces Th2
IL4
What cell types react during initiation of a reaction
DC go to LN —> Naive T cells —> Th2 —> Th2 —> B cells —> basophil, eosinophil, mast cell
What event constitutes sensitization
IgE binding to Fcε on basophils and mast cells
What reaction is seen during sensitization
Nothing
What is released from mast cells during allergies
Tryptase (tight junction rearrangement)
Histamine
De novo synthesis of cytokines
What cell type is central to local and systemic manifestation of food allergies
Mast cells
What is responsible for the local acute GI response (diarrhea) to allergen exposure
PAF and serotonin
Disseminated Ags can trigger what symptoms
Urticaria and brochospasm
Distal reactions of allergies involve what mediators
histamine and PAF
Many children with allergies to cow milk show no reaction with
IgE, they have Type IV delayed type hypersensitivity which is Th1 mediated
What foods are most often associated with anaphylaxis
Peanuts, tree nuts, seeds, seafood, spices, celery, eggs, milk, and some friuts
What are the systemic reactions of anaphylaxis
GI
- increased fluid secretion
- increased peristalsis
Airways
- decreased diameter
- increased mucus
Blood veseels
- increased flow
- increased permeability
What causes the airway constriction in the airways
Bradykinin
Nut induced allergies are also mediated by
IgG
What causes increased vascular permeability and SM contractility
PAF and histamine
What converts C3 and C5 in complement mediated reaction
Tryptase
Wheat allergies are mediated by what
IgE
What is the most common variant of wheat allergies in adults
WDEIA (wheat-dependent exercise-induced anaphylaxis)
People with what are more likely to develop autoimmune diseases
Celiac
What Ab test is positive in those with CD
Anti-tTG2
What are the main HLA genotypes that predispose someone to CD
HLA-DQ2 and DQ8
What do HLA-DQ2 and 8 form a response to
Gluten peptides
Macrophages participate in ______ which DC and B cells participate in
Phagocytosis; endocytosis
Gluten is rich in what AA
Glutamine and proline
What is gluten structure similar to
Collagen
Why is gluten left partially undigested
Lack of prolyl endopeptidases
What causes gluten to become an Ag
Glutamines are deamidated by tissue TG2
The majority of CD patients express what heterodimer
HLADQ2.5
What is responsible for tissue remodeling in CD
MMP1,2,12
Th2 cytokines, in CD, drive the production of auto-Ab to
Gluten and TG2
What cytokines links the adaptive and innate immune response
IL15
Who should be tested for CD
- failure to thrive and persistent diarrhea
- GI symptoms including recurrent abdominal pain, constipation, vomiting
- Non-GI symptoms such as dermatitis herpertiformis
How should you test CD
IgA ab to tTG
If the results from IgA tTG comes back odd, what should you do
Measure total IgA to rule out IgA deficiency
What is recommended to confirm CD in all cases
Intestinal biopsy
If these are missing you can rule out CD
HLA DQ2 or 8
