Food Allergy And Its Mechanism

Published Date: 02 Nov 2017

According to the statistics of Asthma and Allergy Foundation of America, about 50 millions of Americans suffer from allergy. About 6% of them suffer from food and drug allergy. Approximately 30,000 incidence of food allergy occur every year which need to be taken to hospital. More than 200 people die of food allergy every year in America. This reflects that food allergy is quite serious in the world. Therefore, researchers want to find out some method that can cure allergy. This paper is going to review what is food allergy and the new trend of food allergy therapy.

Food allergy and its mechanism

Food allergy belongs to type I hypersensitivity reaction, most common one is acute anaphylaxis. Once patient eats certain type of food that he/she is allergic to, the symptoms, such as inflammation and rash, will appear immediately. The mechanism behind anaphylaxis is that, food molecule acts as antigen. It will be taken up by antigen presenting cell, like dendritic cells. Antigen processing and antigen presentation will take place so that T helper cell will produce IL-4 to induce class switching of B cell. IgE will be produced. IgE will then bind to IgE receptor on mast cell. When the patient is exposed to the same allergen again, antigen will bind to IgE on mast cell, stimulating the release of preformed and newly formed mediators, like cytokine and chemotactic factor, from mast cell. These mediators will cause tissue damage due to blood vessel dilation and the migration of immune cells to affected area.

Conventional treatment of food allergy

Since food allergy is triggered directly with the contact of special type of food, patients are usually advised not to intake the allergic food. If they contact that kind of food, they can still take some drugs to minimize the symptom of food allergy. For example, antihistamines can compete with histamine for histamine receptor as to block the effect of histamine which induces inflammation. Steroids are also used to inhibit vasodilation and the migration of neutrophils and monocytes to the site. Hyposensitization is also method that treat food allergy. It stimulates production of IgG which can compete with IgE for the antigen. Even though these methods can reduce the symptoms of food allergy, they cannot cure food allergy thoroughly.

New therapy on food allergy

Paul Bryce and Stephen Miller from Northwestern University have found that inducing food protein onto immune cells can turn off the immune response towards allergic food in mice. First, they extract white blood cells from the mice. Then, they use peanut protein which chemically attached on leukocytes with ECDI and introduce the leukocytes back to the BALB/c mice. They finally introduce peanut protein into treated mice (WPE-SP) and control mice (WPE). They compare the concentration of IL-4, IgE and eosinophils, and change of body temperature. They found that the concentration of IL-4 in WPE-SP has decreased about three folds from 60 pg/ml to 25 pg/ml when compared to WPE control mice (Fig 1). For IgE concentration, they use ELISA to detect the level of IgE with spectrophotometer. It is observed that WPE contributes about 0.03 OD but it is undetectable in WPE-SP. That means WPE-SP can significantly inhibit the function of Th2 and the class switching of B cell to IgE. With greatly reduced level of IgE, the release of mediators from IgE bound mast cells is also affected. The release of mediators will cause vessel dilation which may lead to significant drop in body temperature. However, it found that the core temperature of WPE-SP only varies within 1℃ while that of WPE fluctuates from 6 to 11 ℃.The research also finds that the concentration of eosinophils in blood has also decreased 4 folds from 1.2x105 cells/ml to 3x104 cells/ml in WPE-SP (Fig 1). All of the result above shows that introduction of peanut protein conjugated leukocytes to allergic mice can minimize the symptom of food anaphylaxis as immune system realizes that peanut proteins are safe to body due to its presentation on immune cells. Therefore, hypersensitivity reaction can’t be triggered.

Figure 1 shows the relative ratio of IL-4 and eosinophils between peanut proteins conjugated leukocytes(WEP-SP) and control(WEP).

Prospect of new therapy

As the mechanism of this therapy is based on conjugating protein onto white blood cells, other proteins of allergen can also be applied, such as pollen, egg and milk. Tradition therapy may have drawback like anaphylactic shock which patients may have high risk on life. However, the chance of getting side effect with this therapy is much lower. Therefore, clinical application needs to develop in order to see whether it is safe for human. If it succeeds in human, this will become the new trend on treating food allergy and food allergy can be cured instead of minimizing the symptoms or avoidance of allergens.