Risk of Allergy from Genetically Engineered Products
Fears of risk of allergy, from products of Genetic Engineering (GE), have become a major issue in biosecurity considerations.
Many proteins are immunogens and antigens, which elicit the production of different types of immunoglobulin (Ig) antibodies in mammalian systems. In response to the presence of immunogens and antigens, immunoglobulin M (IgM) antibodies form first but the quantity of the subsequently formed immunoglobulin G (IgG) antibodies is the highest of all. IgA are involved in the defence of the oral cavity. The function of IgD antibodies, which occur in small quantities, is not well understood. These antibodies fight infection in our body system.
For some unknown reasons, our immunological system reacts to certain proteins in an entirely different way, to produce another class of antibodies, the IgE. These are the allergens.
IgE molecules bind to mast cells in the internal and external linings of the body. The mast cells have large membrane bound organelles containing histamine. The binding of IgE to the mast cells causes the release of histamine triggering an inflammatory reaction, in the tissue layers containing mast cells. Externally, this manifests in the skin as rashes or weals, and internally the gastric lining becomes inflamed, often associated with stomach cramps. Bronchial allergies are caused mostly by inhalants.
While most allergens are proteins, secondary metabolites (haptens), such as penicillin or parthenin, also can cause severe reactions. Haptens need to bind to a carrier protein to be allergenic. Usually this is an endogenous protein, already present in our body.
The best way to avoid allergy is to avoid contact with the allergen, basing on each individual’s experience. Immunological treatment of allergy involves identifying the allergen through dermal tests and introducing it into the body system in small doses over a period of time. Slowly, the body system responds into producing more and more of IgG antibodies, which bind to and neutralise the allergen before large quantities of IgE are produced. Most of us are protected from an innumerable number of allergens by a similar natural process.
Immunological treatment of allergy is not always successful and is not feasible when an endogenous protein is involved, because the body does not produce antibodies to its own protein (except in the case of autoimmune diseases).
Proteins in conventional food items such as fish, eggs, milk, peanuts, Brazil nuts, certain varieties of rice, cucumbers, mushrooms and many others cause allergy in different people and so do certain drugs.
Most products of GE are not potentially more allergenic than their conventional counterparts. The risk of allergy needs to be considered only when a GE food or drug contains one or more new proteins, not present in the isogenic variety, coded by the introduced genes. For example, Bt potato tuber contains the Bt protein, which was found to be safe. When there are no new proteins in a GE product, the question of allergy has no relevance. If some one is allergic to conventional peanuts, the same will happen with GE peanuts as well.
Extensive tests are being conducted to check for allergenicity of GE products. The following considerations need to be kept in mind in this regard: a) tests use only models of known allergenic proteins and do not involve all proteins or probable non-protein allergens, b) it is near impossible to test for all the proteins and non-proteins in a product for the potential of allergy, c) there is no single allergen that can cause allergy in all the people even in a single household, and d) people tend to be allergic to certain substances only during a period of their life and not all through.
Allergy is neither a new nor a universal issue. It is a problem for some individuals and it is not equivalent to an infection. Any chemical substance in the environment or that is ingested into our body system, can be allergenic. Most allergies disappear as mysteriously as they developed. We have not stopped the production of fish, eggs, milk, peanuts, etc., for the reason they cause allergy in some people. What is needed is a rational attitude with concern for larger benefits.
Professor C Kameswara Rao,
Executive Secretary,
Foundation for Biotechnology Awareness and Education,
Bangalore,
India (krao@vsnl.com)
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