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Making immune responses against food components is part and parcel of normal physiology. Whether outcome is normal or not depends on the type of immune responses (see figure below from Berin, M. Cecilia, and Hugh A. Sampson. “Food allergy: an enigmatic epidemic.” Trends in immunology 34.8 (2013): 390-397. http://icahn.mssm.edu/static_fil…).

  • Normal Immune Responses to Food Antigens: As long as antibody classes such as Immunoglobulin A and IgG4, and T cell responses such as Regulatory T cell predominate, outcome is likely to be benign.
  • Abnormal Immune Responses to Food Antigens: Outcome can be pathology if antibody classes other than IgA predominate, especially Immunoglobulin E antibodies, since Antigen-IgE complexes can bind to specific receptors on cells such as Mast cell, resulting in release of potent chemical messengers such as Histamine, which represents the hallmark of typical allergic immune responses. In the case of food antigens, such outcome results in food allergies.