A recent discovery regarding how some food allergies develop may soon lead to testing of medications that would prevent these allergic reactions in the gastrointestinal tract.
Dr. Rothenberg explained that allergic diseases are now occurring in epidemic numbers, affecting almost 30 percent of the population of most countries around the world. “We have not only seen a marked increase in the incidence of allergic diseases (a doubling in recent decades), but the emergence of allergic reactions to common environmental substances has also increased at an alarming rate,” noted Rothenberg, section chief of allergy and clinical immunology in Cincinnati Children’s division of pulmonary medicine, allergy and clinical immunology.
A food allergy occurs when a person’s immune system overreacts to an otherwise harmless food. This hypersensitivity occurs because of an allergic antibody known as IgE (Immunoglobulin E), which is found in individuals with allergies. Allergens, the parts of foods that trigger allergic reactions, are usually proteins found in the food. As many as 90 percent of all allergic reactions are caused by only a handful of food allergens. The most common allergens are the proteins in cow’s milk, eggs, peanuts, wheat, soy, fish, shellfish and tree nuts.
Dr. Rothenberg added, “…food allergies such as peanut anaphylaxis now affect about five percent of the population. These problems are particularly concerning at young ages when adverse reactions to new foods in the diets often becomes a challenging problem”.
Scientists have known for some time that in patients with allergies and allergic asthma, eosinophils, a type of cell normally found in the blood, accumulate in tissue (for example, in the airway or the intestine) as well as the blood. These eosinophils are believed to be at least partly responsible for the inflammation that occurs in the gastrointestinal tract of persons with food allergy; research suggests that inflammation associated with eosinophils found there may also be involved in other disorders such as inflammatory bowel disease and gastroesophageal reflux.
Drs. Rothenberg and Hogan exposed two groups of mice, designed to be food-allergic, to oral allergens, to induce the equivalent of an allergic reaction. They wanted to find out if blocking eotaxin (a protein molecule in the body that pulls eosinophils from the bloodstream and into tissues) would prevent eosinophils from collecting in the gastrointestinal tissue, and if that in turn might prevent gastrointestinal inflammation.
They did this by genetically engineering one group of mice to have no eotaxin. The other group of mice was unchanged in that respect and did produce eotaxin. In the mice with eotaxin, eosinophils were found in the blood as well as the gastrointestinal tract after exposure to food allergens. The mice with no eotaxin did not have eosinophils in the gastrointestinal tract, however eosinophils were increased in the blood.
According to Dr. Rothenberg: “This demonstrates a critical role for eotaxin, specifically in regulating allergic responses in the gastrointestinal tract. Since agents that block eotaxin and similar chemokines are being actively developed by a number of pharmaceutical companies, these studies provide impetus for rapidly applying these new drugs to gut allergy”.