Food allergies affect around 4% of adults and 4-6% of children in the United States. The most common allergic reactions to food are cough, runny nose, sneezing, dizziness, chest pain, rashes, itching, hives, swelling, nausea, vomiting, and diarrhea. Factors that influence food allergies include exposure as a child and breast feeding. Allergic responses can arise from a number of proteins found within any given food. There are thought to be two types of allergic reactions, immune reactions and non-immune hypersensitivity reactions.
Biosignaling plays a major part in the immune reaction response to food allergies. When cells receive and act on signals sent throughout the body, they are communicating through biosignaling. These are the signals that will bring about a response. Intolerance of certain foods creates a reaction within the cells of the body and there are many different kinds of biosignals that can result. They include ligand-gated ion channels, receptor enzymes, g-protein coupled receptors, and steroid receptors.
In food allergy reactions the most common type of biosignaling reaction would be receptor enzymes. Within this process the enzymes demonstrate specificity, amplification, adaptation and integration. Enzymes and signal molecules will fit in a binding site on a complementary receptor; in food allergies certain responses will bind to the site and produce a reaction. The enzymes can also activate a large number of molecules, therefore demonstrating amplification. The feedback produced in this reaction can sometimes desensitize or adapt certain molecules which could explain why some people are not allergic to certain foods as they grow older. And lastly receptor enzymes show integration which is when two signals can have an opposite effect (Sampson 1999). The following exert from an article shows an example of the receptor enzyme process and how scientists can work around allergic reactions. “Insulin has an important role in the treatment of diabetic patients. Further, it can result in undesirable side effects. One of the problems that are associated with insulin therapy is allergic reactions. Although insulin allergy is uncommon, especially in patients with type-2 diabetes, but when it occurs, its management can be difficult. We report a 55-year-old woman with poorly controlled type-2 diabetes and insulin allergy. She revealed hypersensitivity reactions including urticaria and respiratory symptoms, immediately after injection. So, specific immunotherapy with other insulin preparations was done. Finally, after specific immunotherapy, we were able to treat the patient with short- and long-acting analogs successfully (Hasani-Ranjbar et al).”
Using these techniques in regards to food allergies will help scientists discover ways for patients to avoid having reactions to certain foods.
The different chemicals produced by the body from an allergic reaction and the chemicals found in the food are the molecules that will bind to certain receptors in the body. These allergic reactions occur because the biologically active chemicals produced by the immune system are attempting to protect the body from foreign invaders that could harm the body. A food allergy occurs when the body's immune system mistakenly believes that a harmless substance is harmful. In order to protect the body, the immune system creates substances called antibodies specifically for that food. The next time that food enters the body, the immune system releases huge amounts of chemicals, such as histamines, to protect it. These chemicals trigger symptoms that can affect the respiratory and cardiovascular systems, gastrointestinal tract, and skin. Most allergic responses arise as a result of an antibody, known as immunogloubin E (IgE), which reacts to the presence of specific allergens causing a series of immune-related responses. As with all five classes of immunoglobulin, IgE is a Y-shaped protein consisting of four polypeptide chains that are bound together by disulfide bonds. Two heavy polypeptide chains, each comprising approximately one-third of the total mass of the antibody, form the “base” of the Y, which an antibody uses to bind to various effector molecules and cells. The heavy chains continue to cross over at the middle where they each form half of an “arm.” Two light polypeptide chains, running parallel to the arm portions of the heavy chains, make up the other half of the arms. Within the ends of the light and heavy chains on each arm is an antigen-specific binding site wherein variation within each class is found (Janeway et al. 2001). By contrast, the classes themselves vary in the structure of their heavy chains resulting in a variety of physical and functional properties. Specifically, IgE’s heavy chains contain five protein domains, one more than three of the other classes, in place of a flexible hinge region normally found at the branch of the Y. Despite lacking the hinge region found in other classes, IgE suffers no loss in arm flexibility leaving researchers at a loss as to what the specific purpose of this structural difference is. In terms of functional properties, IgE binds to mast cells and basophils with a much higher affinity than the other classes of immunoglobulin, solidifying its role in most allergic reactions (Janeway et al. 2001).
Antigen-presenting cells combine with MHC II molecules to display a portion of a peptide to T-cells. If the T-cell has the specific complimentary receptor, it will then bind to these molecules. This is the beginning of T-cell and cytokine production. These reactions create the signal needed for an IgE response to begin (Sampson 1999). The actual sequence of IgE-mediated hypersensitivity reactions occurs in two phases, requiring an initial exposure to the allergen, known as sensitization, and a second re-exposure upon which a visible immune response is elicited. Sensitization arises when allergens are inhaled and interact with cells such as Langerhans cells found lining the airways. These interactions result in the transformation of B-lymphocytes into plasma cells that then produce IgE antibodies with antigen binding sites specific to the initial allergen. IgE then is circulated throughout the blood stream and to the tissues where the base is able to bind to receptors found on basophils and mast cells, respectively (WAO 2003).
Upon re-exposure to the allergen responsible for sensitization, allergen proteins enter circulation where they are free to bind to the antigen binding sites of IgE resulting in cross-linking between separate mast cells and basophils. This cross-linking causes the degranulation of affected cells, releasing inflammatory mediators like histamine into nearby tissues causing a variety of visible immune responses ranging from sneezing, and increased mucus production to constriction of the respiratory tract and urticaria (Sicherer 2011, p 684).
The non-allergic food hypersensitivity is also referred to as non IgE (Immunoglobulin E) mediated or an intolerance and occurs when the person is not able to break down and digest the food properly. A common example of non-allergic food hypersensitivity is lactose intolerance, which is a hypersensitivity to lactose (lactic sugar) in milk where there’s not enough of the enzyme lactase produced to help absorb the lactose. When looking at the origin of food intolerance, it all comes down to the histamine level. The human cell produces its own histamine from basophils that contains it in the form of granules. The food that is being consumed also has histamine in it as well; some food contains more histamine than others. When the granules are released from the cell, their effect on the body is the contraction of smooth muscle tissues of the lungs, uterus, and stomach. Within the stomach, the blood vessels dilate which increases permeability and lowers blood pressure. This causes the stimulation of gastric acid secretion within the stomach. When there’s an abundance of histamine, the human body is unable to regulate it which causes the symptoms of food intolerance.
What makes food allergy different from intolerance is the abnormal response to a food that is triggered by the immune system. The symptoms of food allergy happen almost immediately when a certain food is consumed. Although both hypersensitivity and true immune reaction often fall under the same topic, they are very different by the way the body reacts to them. The main differences are that non-allergic hypersensitivity reactions are not life threatening, happen gradually, and are sometimes based on amount consumed, whereas food allergies are the opposite and much more severe.
There is no cure for food allergy, but research is ongoing. There are studies that suggest that gradual exposure to some food allergens may allow some tolerance to that food. These challenges should be done only under medical supervision and this possible treatment for food allergy is still being studied. The current recommendation is that the only way to keep from having an allergic reaction is to avoid the food that causes it.