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In 1906, the word allergy was coined by Von Pirquet to describe stages of sensitivity to irritants which were different from the normal. This sensitivity could be either above or below average.
The nature of allergies is still emerging. The exposure to an antigen (foreign substance) results in the production of antibodies. Subsequent exposure results in a reaction between the antibody and antigen, which release histamine. This causes an observable result, which we term allergy. The latest studies indicate that allergies are related to a weak or malnourished immune system, often the result of a malfunction of the body’s immune system.
As we have seen, the immunoglobulins appear in the gammaglobulin protein antibodies. They are distinguished by the abbreviations: Ig. The 4 main classes are: IgE, IgG, Igm, and IgA.
IgG antibodies have two combining sites for antigens, and IgM have 5 to 12 combining sites. IgA immunoglobulin, which appear to be similar to IgG, are more concentrated in the mucous membranes than in the serum.
IgE is the immunoglobulin mostly associated with immediate reactions to substances, and is often responsible for the onset of anaphylaxis.
Allergens such as pollen, dust, mites, molds, etc., encounter mast cells found in the tissues and the ones in the bloodstream, known as basophiles. On the surface of mast cells and basophiles there are specific antibodies called immunoglobulin “E” (IgE). For each mast cell or basophil, there could be thousands of IgE molecules.
Let’s say an allergen, such as mold, encounters a basophil or a mast cell. In addition, let’s say that the cell has certain pollen antibodies on its surface. The biochemical reaction which takes place secretes granules which contain mediators – chemical substances which actually react with the tissue of the body and cause allergic reactions.
With a weakened immune system, an overreaction can produce the allergic antibodies. The IgE antibodies attach themselves to, say, the upper respiratory tract lining, and when IgE antibodies and the nasal respiratory system cells unite, histamine is released causing the unpleasant symptoms, known as a cold.
Sensitization occurs, when the immune system learns to respond to these allergens as if they were dangerous. Each time exposure to a certain allergen occurs, the system reacts with a full attack. Almost any element of our daily life can provoke the symptoms of allergy for the hypersensitive.
As discussed, an immune complex is the combination of an antigen and antibody. This is where the phagocytic – macrophages, polymorphs, eosinophils, etc. – activity occurs.
In some cases, complexes may persist in circulation and cause inflammatory damage to organs or inhibit useful immunity, such as against parasites. The detection of complexes and the identification of the antigen in them is therefore important.
The antibody response is a dramatic manifestation of adaptive immunity, where pre-existing populations of B-cells are stimulated to divide and secrete large amounts of specific antibody. This usually results in the elimination of the stimulating antigen and leaves the body ready for subsequent contact with the same antigen.
Allergens are antigens that can trigger extreme physical reactions which could result in anaphylaxis. IgE is the major class of antibody, and levels of it in the body can be up to 30 times higher in allergic patients.
The type of allergic reaction previously mentioned is an immediate response, that is, not delayed. IgA, antibody protects the skin and mucous surfaces, and a deficiency of IgA is thought to facilitate entry of antigens and stimulation of IgE. IgG antibody, can protect against mast cell degranulation by efficiently removing antigens. There are four IgG subclasses (IgG1, IgG2, IgG3, IgG4).
Allergic diseases such as hay fever and asthma, which are usually due to plant or animal allergens, are generally a result of IgE excess. An example of an IgE allergy is hay fever, affecting the mucous membrane of the eye, nose, and upper part of the lungs. This is almost always due to tree pollen in the air during spring, while during summer it is usually caused by grass pollen. In autumn, fungus spores are usually responsible for the trigger of allergic responses.
Asthma has been called the hay fever of the bronchus. It is thought to also be an allergic response and this theory has been under debate over the years. The allergic reaction is similar and the local release of histamine results in the swelling of the mucous membrane. Difficulty in breathing, due to edema, is what often occurs.
There are 2 kinds of categorized asthma, one intrinsic, where the precipitating cause is an infection of the respiratory tract, and the other an extrinsic asthma, where the continued inhaling of dust or pollen is the infecting agent.
A food sensitivity (allergy) is any adverse reaction to a food or food component involving the body’s immune system. It is important to note that some adverse reactions to foods do not involve the immune system. These are known as food intolerance, such as food poisoning or the inability to properly digest certain food components such as lactose, contained in milk products.
A true allergic reaction to a food involves three primary components:
It was Hippocrates who recognized that food sensitivities occurred, as he observed that milk might cause gastric upset and urticaria. Since the 1970’s it has been observed that there has been an increase in food-causing allergies among Americans. It is thought that this is due to new environmental changes, increased ingestion of less nutritious food, and chemical pollution within the food chain.
According to the Academy of Allergies and Immunology, there are different definitions for allergies. First, the adverse reaction or sensitivity is a general term which can be applied to a specific ingested food.
Food hypersensitivity, or food anaphylaxis, (allergy) is an immunological reaction which involves IgE. Food intolerance is an abnormal physiological response to an ingested food, but may not be immunological (involving IgG), rather it could be an idiosyncratic response. Food poisoning implies that there is an adverse effect as a result of a direct action of food which might involve microorganisms or parasites contaminating the food.
In addition to the above definitions an allergy to a particular food might develop with frequent consumption of it. For example, the “cyclic allergic” form is the most common which develops over time by repetitive ingestion of the same food. Fixed allergies are sensitivities which occur whenever a food is eaten, even once.
Immune mediated sensitivity is also an allergy, as it is an interaction between food antigens, histamines, mast cells, basophiles. In this type, IgE and IgG are also found. Thus, the immune system controls most of the food allergies found.
Common physical symptoms or clues of delayed food allergies might be dark circles or puffiness under the eyes, chronic headaches, gastrointestinal disorders or bloating, cramping, or sinusitis. Symptoms such as vomiting, blurring of vision, or swelling might be more characteristic of immediate allergic responses.
In brief conclusion, when an unwanted substance enters the body for the first time regardless whether its a virus, bacteria, toxin, drug, or incompletely digested food, the body starts the antibody process. The immune system’s defenses are called out, and the immediate reaction stimulates the IgE response or a delayed reaction incites the IgG response.
Some individuals experience immediate allergic symptoms when exposed to pollen, dust, animal dander and foods, and, as we saw, can be classified as IgE responses. It is generally easy to diagnose an immediate response; for example, an allergy to strawberries can be indicated by lip swelling every time a strawberry is eaten.
Previously skin testing with its discomfort and possible anaphylactic reaction was the only testing method. Now serum testing is a more convenient way to detect the IgE and IgG specific allergens. According to a American Academy of Allergies and Immunology 1992 position statement, “In principle, in vitro tests for IgE constitute a technically valid method for detection of allergen-specific IgE antibody in serum.” For a complete clinical picture the total workup could include IgE and IgG testing, and this would give the physician enough data to treat without having to guess.
Testing for delayed food allergies is a relatively new practice because there has been an academic debate over the significance of IgG, and the subsets being able to identify toxic insults. However, the traditional establishment is beginning to recognize that food allergies can be detected through serum.
A serum will carry an Ig when first a type of free floating antibody called secretory IgA is released into the digestive tract. It then goes to the bile ducts into the upper duodenum, and here the offending foods are prepared with a coating before they enter the small intestine from the stomach. IgA acts as a protectant, a result which is beneficial, but not unlimited. Therefore if a person is repeatedly eating a toxic food the secretory IgA will be taxed and the immune system will begin to show signs and symptoms.
Simply stated, the toxic food gets improperly digested, and the compromised chemical mediator allows the food to pass into the bloodstream. Once in the bloodstream another immunoglobulin, IgG, is released, attaching itself to all oversized macromolecular food particles entering the bloodstream. Again, when overtaxed, the IgG’s can no longer purge the system well. When the circulating immune complexes eventually penetrate the walls of capillaries and are deposited in tissue, inflammation can occur. Other manifestations also clinically present themselves.
Symptoms of immune response can include inflammation, pain, swelling and cellular damage. Cell damage occurs due to immune protein substance, a complement which promotes the release of chemical mediators and free radicals. Consequently a patient can continue to aggravate the immune system by eating hostile allergic foods which become pathogenic and penetrate intestinal walls. Hence, testing for delayed food sensitivities is most often measured through serum, where the IgG’s reside.
To review, the IgG’s have been broken down into the four subclasses as we have already seen and tests can measure the antigen-antibody for toxic foods which have delayed onset: IgG1, IgG2, IgG3, IgG4. Most of the antibodies are seen in IgG3.
Some laboratories only perform IgG1, which unfortunately is limited in its final data. Other laboratories test for IgG1 and IgE combined. The results of this test again potentially miss valuable information from the IgG2 and IgG3.
Delays from the food allergy antigen can take up to several months to obtain clinical significance. When testing for food allergies, IgE is a very small part of the total picture as it only shows the immediate response. Many reactions, especially in adults, are not due to immediate hypersensitivity (type one IgE) reactions. Statistically speaking it has been estimated that only 10% of the population have the type I or IgE mediated or immediate allergic response. This is in contrast to the 80% who have a delayed symptom onset which is termed as food sensitivity, or delayed allergy. The causes of adverse reactions to foods are more difficult to determine than IgE mediated reactions to inhalants. Again, IgE only gives a small, but sometimes necessary, picture of the whole.
One testing method is known as the ELISA method, which is based on a non-isotopic modification of the RAST method and permits simultaneous determination of a patient’s IgG level. A method for the detection of HIV antibody to the AIDS virus is tested by a similar technique, that is, through ELISA. A person who tests positive for HIV antibodies by two different kinds of lab tests is said to be HIV positive.
In summary, it has been found that the data on IgG antibodies specific to foods has been useful in the diagnosis and treatment of patients with a wide diversity of symptoms. The majority of clinical IgG’s show up in the subset IgG’s 3 and 4. We know that the clinical reactions to foods may be delayed for periods of time, making determination of the offending foods difficult. Therefore the measurement of specific IgG antibodies to foods may prove to be useful in helping food sensitive patients. There is always the possibility that where there are large amounts of circulating IgG antibodies, that immune complex formation may occur; these complexes may deposit in certain tissues.
An IgG allergy profile is run by adding patient serum to all allergen coated wells in a specially designed plate. The serum is then incubated, and in that process IgG binds to the allergen coated wells. After the incubation period, the plates are washed with a buffer to remove unbound serum. Then the wells are filled with an enzyme-labeled antibody which couples with the IgG and is bound to the wells. After a final buffer-wash the plates are filled with a freshly prepared substrate, and the intensity produced from the reaction is proportional to the concentration of allergen specific IgG. The final steps involve the use of spectra-photometer.
Other methods of laboratory testing which measure immune complexes are: Rast, FICA, Cytotoxic, EVA, kinesiologic, fasts or elimination, and skin testing. Some of these methods are experimental with little positive predictive accuracy and a poor scientific basis.
Examples of possible food related allergy symptoms or conditions as clinically observed and published are as follows: Acne Vulgaris, allergic sore throat, arthritis, asthma, attention deficit disorder, bulimia, candidiasis, chronic constipation, chronic fatigue, crohn’s disease, conjunctivitis, depression, delusions, dyslexia, edema, epilepsy, fever, gastric and duodenal ulcerations, hay fever, hoarseness, insomnia, irritable bowel syndrome, juvenile rheumatoid arthritis, memory loss, malabsorption syndrome, obesity, otitis media, premenstrual syndrome, psoriasis, rheumatoid arthritis, tinnitus, and vertigo. Celiac Disease is another food induced illness which is caused by gluten found in wheat or rye flour. It is thought that the protein in the gluten acts as the allergen.