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B. Mechanism of Allergic Reaction An allergic reaction stems from an abnormal, or exaggerated, immune system response to specific antigens, which in foods are proteins (Sampson, 1999). This immune response occurs in two phases, an initial “sensitization” to an allergen and the “elicitation” of an allergic reaction on subsequent exposure to the same allergen. Sensitization occurs when a susceptible individual produces IgE antibodies against specific proteins in a food. Upon re-exposure to the same food, the allergenic proteins bind to IgE molecules on immune mediator cells (basophiles and mast cells), leading to activation of these mediator cells. This elicitation causes the release of inflammatory molecules (e.g., leukotrienes and histamine). The specific effects that are seen and the severity of an allergic reaction are affected by the concentration and type of allergen, route of exposure, and the organ systems involved (e.g., skin, GI tract, respiratory tract, and blood) (Taylor and Hefle, 2001).

Sensitization

Food Allergen

B-Cells and T-Cells

IgE Production

Elicitation

IgE

Mast Cells

Food Allergen

Activated Mast Cells

Release of Mediators

Allergic Reaction

Figure II-2. Mechanism of Allergic Reactions

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