<p>Consumption of a normal diet stimulates cells in the gut that suppress rejection of food by the immune system, scientists have found, explaining why some children are more susceptible to food allergies.<br /><br /></p>.<p>Food allergy or intolerance can cause symptoms ranging from a harmless skin rash to a potentially lethal anaphylactic shock.<br /><br />Researchers from La Jolla Institute for Allergy and Immunology (LJI) in US have explained how food tolerance emerges over time in normal individuals.<br /><br />Coupling molecular approaches with a long-forgotten model of 'antigen-free' mice, the study is the first to demonstrate that consumption of a normal diet stimulates cells in the gut that suppress rejection of food by the immune system.<br /><br />Knowing this could explain why children, who have more limited exposure to novel foods than adults, are more susceptible to food allergies.<br /><br />Like pathogens, food displays macromolecular markers known as antigens that announce to the immune system that food is 'foreign'.<br /><br />Previous analysis of how the body distinguishes antigenic friend from foe revealed that feeding lab mice a novel test protein - for example, the egg protein ovalbumin - induced development of immunosuppressive T-regulatory, or 'Treg' cells, in the gut, which then acted to block the immune response to that particular protein.<br /><br />Researchers re-established 'antigen-free' mouse models designed to represent an immunological blank slate.<br /><br />These animals were not only raised in a germ-free environment but were also fed an 'elemental' diet of amino acids, the building blocks of proteins, rather than foods that contain intact proteins themselves.<br /><br />The mice were, in essence, immunologically naive, because the amino acid building blocks are too small to be recognised by the immune system.<br /><br />These mice therefore have little or no prior contact with antigenic proteins and other macromolecules. Using molecular marker analysis, researchers found that antigen-free mice were depleted of Tregs in the small intestine whereas a large number of these Tregs were present in germ-free counterparts fed a 'normal' protein diet.<br /><br />That difference alone suggested that proteins contained in food stimulate Treg development.<br />It also hinted that Tregs present in the gut of normal mice might suppress a potentially disastrous immune response to those proteins.<br /><br />"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," said Charles Surh from LJI.<br /><br />The study suggests what happens on a cellular basis as some children outgrow it - they may be expanding their repertoire of Tregs that recognise new foods as 'safe'. The findings were published in the journal Science. <br /></p>
<p>Consumption of a normal diet stimulates cells in the gut that suppress rejection of food by the immune system, scientists have found, explaining why some children are more susceptible to food allergies.<br /><br /></p>.<p>Food allergy or intolerance can cause symptoms ranging from a harmless skin rash to a potentially lethal anaphylactic shock.<br /><br />Researchers from La Jolla Institute for Allergy and Immunology (LJI) in US have explained how food tolerance emerges over time in normal individuals.<br /><br />Coupling molecular approaches with a long-forgotten model of 'antigen-free' mice, the study is the first to demonstrate that consumption of a normal diet stimulates cells in the gut that suppress rejection of food by the immune system.<br /><br />Knowing this could explain why children, who have more limited exposure to novel foods than adults, are more susceptible to food allergies.<br /><br />Like pathogens, food displays macromolecular markers known as antigens that announce to the immune system that food is 'foreign'.<br /><br />Previous analysis of how the body distinguishes antigenic friend from foe revealed that feeding lab mice a novel test protein - for example, the egg protein ovalbumin - induced development of immunosuppressive T-regulatory, or 'Treg' cells, in the gut, which then acted to block the immune response to that particular protein.<br /><br />Researchers re-established 'antigen-free' mouse models designed to represent an immunological blank slate.<br /><br />These animals were not only raised in a germ-free environment but were also fed an 'elemental' diet of amino acids, the building blocks of proteins, rather than foods that contain intact proteins themselves.<br /><br />The mice were, in essence, immunologically naive, because the amino acid building blocks are too small to be recognised by the immune system.<br /><br />These mice therefore have little or no prior contact with antigenic proteins and other macromolecules. Using molecular marker analysis, researchers found that antigen-free mice were depleted of Tregs in the small intestine whereas a large number of these Tregs were present in germ-free counterparts fed a 'normal' protein diet.<br /><br />That difference alone suggested that proteins contained in food stimulate Treg development.<br />It also hinted that Tregs present in the gut of normal mice might suppress a potentially disastrous immune response to those proteins.<br /><br />"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," said Charles Surh from LJI.<br /><br />The study suggests what happens on a cellular basis as some children outgrow it - they may be expanding their repertoire of Tregs that recognise new foods as 'safe'. The findings were published in the journal Science. <br /></p>