Dr Claudio Nicoletti and his team at the Institute of Food Research in Norwich have discovered that when certain dendritic cells in mice do not produce the immune system molecule Interleukin-12 (IL-12), it makes them susceptible to food allergies.

"We have identified a molecule that is very important for the regulation of immune response and for the first time clearly represents a potential target for the therapy of allergy. This is currently under investigation," said Dr Nicoletti.

In people with food allergies, the immune system responds to food proteins as if it were harmful, producing antibodies to destroy it. In severe cases with some foods, such as nuts or fish, the individual can suffer life-threatenting reactions, including anaphylactic shock.

Currently, there is no way to treat these allergies and sufferers are forced to just be extremely careful about what they eat. Many also carry adrenaline injections in case of contamination.

Dr Nicoletti suggested that by delivering an allergen in the presence of IL-12, allergic reactions could be brought back under control.

"A food protein can be perfectly harmless to one person and lethal to another," he said. "We have identified the missing molecule that normally keeps immune responses under control and appropriate."

Dr Nicoletti, in collaboration with scientists at the University of Siena, compared the activity of dendritic cells in the gut and in the spleen of allergic and allergy-resistant mice. He found that in the gut of susceptible mice, dendritic cells have stopped producing IL-12.

Normally, the dendritic cell presents an antigen to receptor on T-cells, a T-cell receptor, and secretes IL-12. This causes the helper T cells to being producing their own cytokines, such as tumour-necrosis factor-beta (TNF-beta) and interferon-gamma (IFN-gamma). These then attract other immune system cells called macrophages, to kill the pathogen they have engulfed.

Its ability to induce an immune reaction has led to IL-12 being investigated as a potential anticancer therapy. Others have tried to block its action with antibodies to treat problems caused by an over-active immune system - such as the inflammation seen with psoriasis.

This latest study is published in today's issue of the Journal of Allergy and Clinical Immunology.

David Reading, director of the Anaphylaxis Campaign, said: "Food allergy can place an extremely heavy burden on the families affected. We welcome this research and look forward to further developments."