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Study unravels why children are more prone to food allergies

Posted:  Wednesday, March 16, 2016

Study decodes the mechanism for food allergy in children

Allergic reaction to food is a common phenomenon in children. Food allergy has diverse manifestations that may range from a simple skin rash to a fatal anaphylactic shock. Now, a new study provides interesting insights on why children are more susceptible to food allergies than adults and how they outgrow them.

Published online in the journal Science, the preclinical study sought to investigate the intricate mechanisms involved in the development of food allergies and food tolerance in normal individuals. The study looked at the role of immunosuppressive T-regulatory, or "Treg" cells. The researchers employed “antigen-free" mice for the study. The mice, reared in a germ-free environment, were fed a diet consisting of amino acids and had little or no exposure to antigenic proteins and other macromolecules. The researchers compared these immunologically naïve mice with the germ-free mice fed a "normal" protein diet.

The study found large populations of immunosuppressive Tregs in the small intestine of germ-free mice fed the normal diet, but no such cells in the intestine of the antigen-free mice. This meant that proteins present in food triggered the development of Treg cells in the gut of mice fed the normal diet. These Treg cells may have averted a strong immune response to the food proteins.

The researchers also demonstrated the immune reaction to food proteins in antigen-free mice. They transferred "reporter" T cells into antigen-free mice and then fed the animals ovalbumin, a protein they had never been exposed to before. The mice experienced a massive immune reaction to ovalbumin compared to germ-free mice fed a normal diet. The researchers hold the view that the absence of immunosuppressive Tregs in the antigen-free mice led to this reaction.

This study explains why children, who have more limited exposure to novel macromolecules compared to adults, are more likely to develop food allergies. The study also suggests what happens on a cellular basis as some children outgrow the food allergy by expanding their repertoire of Tregs that recognise new foods as ’safe’.

Dr Charles Surh, PhD, the study author and researcher at La Jolla Institute for Allergy and Immunology (LJI) said, "Our work shows food tolerance is acquired and involves specific populations of T cells that develop following its consumption. Without them, we would mount a strong immune response to macromolecules contained in food. We are now examining the cellular and molecular details of how the 'default' strong T cell response to food is regulated. In this context, we plan to pay particular attention to certain foods, such as peanut, egg and other foods that cause food allergy."

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