CLT Food Sensitivities & Immunology Basics 2 — Questions and Answers
Question 1: Which immune cell is the primary effector in IgE-mediated food allergy reactions and releases histamine upon antigen binding?
- Cytotoxic T cell
- Mast cell (Correct answer)
- Neutrophil
- Regulatory T cell
Correct answer: Mast cell
Mast cells bound with IgE antibodies degranulate and release histamine and other mediators when cross-linked by food allergens.
Question 2: In the LEAP protocol, the MRT blood test measures the change in which cellular parameter to identify reactive foods?
- Antibody titer levels
- White blood cell and platelet volume after incubation (Correct answer)
- Eosinophil count in whole blood
- Serum histamine concentration
Correct answer: White blood cell and platelet volume after incubation
MRT quantifies the shift in white blood cell and platelet volume when blood is incubated with food antigens, reflecting mediator release.
Question 3: Which class of hypersensitivity reaction is NOT mediated by antibodies and instead relies on sensitized T lymphocytes?
- Type I (anaphylactic)
- Type II (cytotoxic)
- Type III (immune complex)
- Type IV (delayed) (Correct answer)
Correct answer: Type IV (delayed)
Type IV hypersensitivity is cell-mediated, involving T lymphocytes rather than antibodies, and reactions appear 24–72 hours after exposure.
Question 4: Secretory IgA (sIgA) in the gut serves as the first line of adaptive immune defense primarily by:
- Activating the complement cascade
- Neutralizing antigens in the gut lumen before mucosal penetration (Correct answer)
- Opsonizing pathogens for phagocytosis
- Triggering mast cell degranulation
Correct answer: Neutralizing antigens in the gut lumen before mucosal penetration
Secretory IgA coats food antigens and pathogens in the intestinal lumen, preventing them from binding to and crossing the mucosal epithelium.
Question 5: A patient with increased intestinal permeability ('leaky gut') is at greater risk for food sensitivities because:
- Gastric acid production decreases significantly
- Undigested food peptides cross the epithelium and trigger immune responses (Correct answer)
- Pancreatic enzymes become overactive
- Bile acid absorption is impaired
Correct answer: Undigested food peptides cross the epithelium and trigger immune responses
Tight junction dysfunction allows large, undigested food peptides to enter the lamina propria, where they are recognized as foreign antigens and drive immune sensitization.
Question 6: Which cytokine is primarily responsible for driving the Th2 immune response that underlies IgE sensitization to food allergens?
- IFN-γ
- IL-12
- IL-4 (Correct answer)
- TNF-α
Correct answer: IL-4
IL-4 promotes B cell class switching to IgE production and Th2 differentiation, which is central to atopic food allergy development.
Question 7: Eosinophilic esophagitis (EoE) is distinguished from classic IgE-mediated food allergy in that it is primarily driven by:
- IgE antibodies to aeroallergens only
- Th2-mediated eosinophil infiltration independent of specific IgE (Correct answer)
- IgG4 immune complexes in esophageal tissue
- Mast cell tryptase activity
Correct answer: Th2-mediated eosinophil infiltration independent of specific IgE
EoE is a Th2 inflammatory disorder with eosinophil accumulation in the esophagus; it often involves food triggers but is not strictly IgE-mediated.
CLT Food Sensitivities & Immunology Basics 2
Which immune cell is the primary effector in IgE-mediated food allergy reactions and releases histamine upon antigen binding?