Food allergy mechanism comes to light

- Last updated on GMT

Related tags: Immune system, Allergy

New research from the UK suggests an immune system malfunction
could play a profound role in the onset of food allergies. As the
European food industry gets to grips with imminent rules on the
labelling of allergens, the UK findings will help industry and
consumer alike.

Escalating incidences of food allergies in Europe and the desire to avoid potentially harmful consumer confusion underpinned changes to the Labelling Directive 2000/13/EC due to enter into force in November 2004. The changes herald the mandatory inclusion on food labels of the most common food allergen ingredients and their derivatives: cereals containing gluten, fish, crustaceans, egg, peanut, soy, milk and dairy products including lactose, nuts, celery, mustard, sesame seed, and sulphites.

According to the European Federation of Allergy and Airways Diseases Patients' Associations, estimated 4 per cent of adults and 8 per cent of children in the European Union - the total population equals over 380 million - suffer from food allergies.

While the cause of food allergies has remained a challenge for science, a team of scientists, led by the Institute of Food Research (IFR)​ in the UK, found that two types of cells stop communicating. This means that the programmed cell death of one type of cell fails to happen. Programmed cell death is one of the most important mechanisms for maintaining health in mammals.

"There are two stages to food allergy", said research leader Dr Claudio Nicoletti at the IFR. The first is sensitisation, when the immune system starts producing an antibody in response to eating a food. The second is when that food is eaten for a second time, triggering an allergic reaction.

"We have identified an immune response malfunction that occurs in the sensitisation stage, which could provide a target for future therapies," he said.

There is no current cure for food allergy and vigilance by an allergic individual is the only way to prevent a reaction. In allergic reactions the body overproduces the antibody IgE causing many symptoms including skin rashes, wheezing, sneezing, swelling around the lips, bloating, vomiting and diarrhoea. In extreme cases it causes anaphylaxis, a life-threatening reaction triggered within minutes.

Two critical cells types for regulating immune response are dendritic cells and T-cells. Dendritic cells are white blood cells with fine branches called dendrites. They are stationed at parts of the body most likely to come into contact with pathogens, particularly the skin and mucous membranes. They capture a section of any foreign body, deliver it to other immune cells such as T-cells and instruct these cells to deal with the intruder.

A class of T-cells called T helper 2 cells (Th2) was thought to play an important role in sensitisation to harmless substances including food. But research by IFR scientists questioned this assumption, so they shifted focus for the current study.

No one had looked at the communication between dentritic cells and T-cells in food allergy. Once dendritic cells have given their instruction, they normally die. The scientists found that in allergy, dendritic cells escape death. This could mean that they keep on activating T-cells to create antibodies.

"Dendritic cells are one of the most fascinating cell types in the immune system,"​ said Dr Nicoletti. "It appears that in allergy they get out of control, and this malfunction could have a profound effect on the development of food allergies."

Welcomed by allergy associations, last November Europe confronted the food industry with new rules - to enter into force in November 2004 - on food allergen ingredients when Brussels cleared Directive 2003/89/EC, amending Directive 2000/13. Food manufacturers will have to list all sub-ingredients of compound ingredients, which means that allergens cannot be 'hidden', heralding an end to the 20 year old 25 per cent rule with all ingredients labelled, regardless of the quantity contained in the finished food.

Europe's risk assessment body, the European Food Safety Authority (EFSA) recently concluded that current scientific evidence is 'insufficient to establish an intake threshold' for food allergens.

Cereals, peanuts, soy and dairy products were among a range of potential allergens investigated by the Dietetic Products, Nutrition and Allergies (NDA) panel, part of EFSA, at the request of the Commission. Their findings show 'ample evidence' to justify a list of allergenic ingredients and their derivatives on the food label.

"In no case is the available evidence sufficient to establish an intake threshold below which allergic reactions are not triggered, or to predict reliably the effect of food processing on allergenic potential,"​ said Professor Albert Flynn, chair of EFSA's NDA panel.

Full findings of the IFR led study conducted with the University of Sienna, Italy are published in the Journal of Allergy and Clinical Immunology (Vol. 113, No. 5, May 2004, pp965-972).

Related topics: Science, Food Safety & Quality

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