Discovery of immune system malfunction that plays a profound role in food allergy

Food allergy can be life threatening, but understanding the cause has remained a challenge for science. The international team has found that two types of cells stop communicating. “Either they are not listening to each other or they stop talking”, said research leader Dr Claudio Nicoletti of the IFR. 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 Dr Nicoletti. “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. “They are also one of the most difficult to study, because they are extremely adaptable and exist in very low numbers in the blood. It appears that in allergy they get out of control, and this malfunction could have a profound effect on the development of food allergy”.

The research is published in the Journal of Allergy and Clinical Immunology on Friday (Vol. 113, No. 5, May 2004, pp965-972) and was conducted in association with the University of Siena. It was funded by the IFR’s core strategic grant from the BBSRC and is part of ongoing work to investigate the mechanisms involved in immune response to allergy.

The mission of the Institute of Food Research (http://www.ifr.ac.uk) is to carry out independent basic, and strategic research on food safety, quality, nutrition and health. It is a company limited by guarantee, with charitable status, grant aided by the Biotechnology and Biological Sciences Research Council (BBSRC).