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IMM Exam 2 > Food Allergies > Flashcards

Food Allergies Flashcards

1
Q

Food allergy

A

Adverse health effect arising from a specific IMMUNE RESPONSE that occurs REPRODUCIBLY on exposure to a given food

Can be IgE-mediated or non-IgE mediated

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2
Q

Food intolerance

A

Non-immunologic adverse reactions to foods

Ex: lactose intolerance, rxns to food additives/preservatives, pharmacological effects of caffeine

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3
Q

Food sensitization

A

Presence of food-specific IgE

NOT equivalent to food allergy - just bc you have specific IgE doesn’t mean you’re allergic to the food

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4
Q

Most common food allergens in USA

A

Milk, eggs, peanuts

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5
Q

Risk factors for food allergy

A

atopic dermatitis (eczema)

sibling w food allergy (peanut)

delayed dietary introduction (pearnut)

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6
Q

Two phases of Development of Food Allergy

A

(1) Allergen sensitization

(2) Mast cell activation

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7
Q

Allergen sensitization (process)

A
  1. First exposure to food allergen: taken up through GI tract and phagocytosed by Dendritic cell
  2. Dendritic cell travels to lymph node; presents antigen to Naive CD4+ T cell
  3. Activated CD4+ T cell differentiates into IL-4 producing Tfh cell – stimulates B cell to class switch and make IgE against the antigen
  4. B cell turns into an IgE-secreting plasma cell that secretes peanut-specific IgE
  5. IgE produced by B cell binds to FcgammaR receptors on mast cells

The Mast cell is now “primed” or ready for antigen (peanut) bonding for the second exposure

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8
Q

Mast cell activation (process)

A
  1. Upon next exposure to antigen, the binding of the antigen (peanut) to the IgE (already bound to the Fc receptor of mast cell) ACTIVATES the mast –> degranulation
  2. Activated mast cell releases a variety of mediators: (1) Vasoactive amines, lipid mediators and (2) Cytokines
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9
Q

Function of Vasoactive amines, Lipid mediators released by mast cells

A

Immediate hypersensitivity reaction (minutes after repeat exposure to antigen)

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10
Q

Function of Cytokines released by mast cells

A

Late-phase reaction (2-4 hours after repeat exposure to antigen)

involves recruitment of inflammatory cells

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11
Q

IgE

A
  • Low levels in plasma (<1 microg/ml)
  • Elicited by allergens in atopic individuals (IL-4 production by allergen-specific T helper cells stimulate B cell antibody class switching to IgE)
  • Binds to high-affinity Fc epsilon receptor (FcepsilonR) on mast cells and basophils
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12
Q

Fc epsilon Receptor

A
  • Highly expressed on mast cells and basophils
  • Very high affinity for IgE (full receptor occupancy under normal conditions)

-Composed of:
1 alpha chain (IgE binding)
1 beta chain and 2 gamma chains (Signal transduction)

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13
Q

Mast cells

A

Found in Tissues

  • derived from bone marrow precursors
  • located in mucosal and connective tissues
  • express high levels of FC epsilon receptor
  • Granules contain preformed mediators that are rapidly released upon activation (degranulation)
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14
Q

Growth factors for Mast cells

A

stem cell factor, IL-3

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15
Q

Inflammatory mediators produced by Mast cells upon activation

A

Lipid mediators (prostaglandins, leukotrienes)

Cytokines (TNFalpha)

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16
Q

Basophils

A

Found in Blood

  • derived from bone marrow precursors
  • rare; found in circulating blood (<1%)
  • recruited to tissues during allergic inflammation
  • express high levels of FC epsilon receptor
  • exact role in immediate hypersensitivity rxns unclear
17
Q

Growth factors for Basophils

A

IL-3

18
Q

Eosinophils

A

Recruited to tissues during late-phase of allergic response

  • derived from bone marrow precursors
  • found in circulating blood (2-4% blood leukocytes)
  • increased during allergic disease and parasitic infections
19
Q

Growth factors for Eosinophils

A

IL-5

20
Q

Major granule contentes of Eosinophils

A

Major basic protein, eosinophil cationic protein

enzymes that cause tissue damage (peroxidases, hydrolases, lysophospholipases)

Toxic to microbes and host tissues

21
Q

Mast cell activation by allergen upon second exposure

A

Allergen-triggered cross-linking of IgE-Fc epsilon Receptor complexes results in mast cell activation and degranulation

22
Q

Outcomes of Mast cell activation

A

(1) Granule release of vasocative amines and proteases (leads to vascular dilation/smooth muscle contraction and tissue damage)
(2) Enzymatic modification of AA leading to secretion of lipid mediators (Prostaglandins for vascular dilation and LTs for smooth muscle contraction)

Later….
(3) Transcriptional activation of cytokine genes leading to cytokine release (results in inflammation and leukocyte recruitment)

23
Q

Allergic responses consist of _______ and ________ reactions

A

immediate; late-phase

24
Q

Immediate phase of Allergic response

A

Release of preformed vasoactive mediators by mast cells

  • vasodilation
  • swelling (edema)
  • itching (pruritus)
  • bronchoconstriction
  • intestinal hypermotility
25
Q

Late phase of Allergic response

A

Production of cytokines and chemokines

  • accumulation of inflammatory cells (eosinophils, basophils, T cells)
  • tissue inflammation
26
Q

Benefits of Skin prick testing

A
  • High sensitivity but moderate specificity (lots of false positives)
  • Rapid and safe
27
Q

Treatment for food-induced anaphylaxis

A

Intramuscular epinephrine (first and most important)

Bronchodilators for wheezing/bronchospasm

Antihistamines, gluccocorticoids

28
Q

Oral allergy syndrome (i.e. pollen-food allergy syndrome)

A
  • Presents in adolescents/adults with allergic rhinitis (hay fever)
  • IgE-mediated rxn against pollen-related proteins in food
  • can cook food to degrade allergens
29
Q

Food-dependent exercise-induced anaphylaxis

A

development of anaphylaxis symptoms during exercise that occurs within a few hours of eating a specific food

30
Q

Delayed allergic reactions to mammalian meat

A

Due to IgE specific for the carbohydrate “alpha-gal”

Allergic symptoms occur 4-6 hrs after consuming mammalian meat

31
Q

IgE-mediated food allergy is a type of

A

immediate hypersensitivity reaction

32
Q

Symptoms of IgE-mediated food allergy

A

Cutaneous symptoms (urticaria, angioedema, flushing, itching)

Gastrointestinal symptoms (vomiting, severe nausea and abdominal cramping)

Respiratory symptoms (rhinorrhea, laryngoedema, dyspnea, wheezing/bronchoconstriction)

Cardiovascular symptoms (lethargy, hypotension, syncope)

IMM Exam 2 (15 decks)

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