Common hypersensitivity reactions: Anaphylaxis

Common hypersensitivity reactions: Anaphylaxis
Allergy is a major health problem that is commonly seen in people. India has witnessed an increase in various forms of allergic reactions from 10% to 30% since last 4 decades. Allergy may be caused due to many reasons but majorly found allergens are due to the food substances. In scientific term, an allergy is an immune dysfunction literally known as “hypersensitive reaction”, it is defined as the violent reaction of the immune systems leading to severe symptoms on exposure to allergens. The prime function of an immune system is to protect our system from foreigners. However, in hypersensitive conditions this immune system becomes injurious to the host and in such conditions, it is termed as “destructive process”. The factor causing hypersensitivity is called as an allergen. Hypersensitivity responsible agent called as allergens are numerous; they can be either extrinsic (introduced from outside environment into the body) or intrinsic factor (that occurs within the body itself); some of the allergens commonly seen among the people are the drugs (e.g. penicillin), airborne particles (e.g. dust, perfume, etc.), foodstuffs (such as orange, brinjal, coloured foodstuffs, etc.) and infectious organisms (such as bacteria and parasites). The reaction produced as a result of allergens may manifest immediately or get delayed.

There are different types of reactions produced; some of them include anaphylaxis, serum sickness, Mantoux reactions, transfusion reactions and Arthus reaction. Out of these reactions, anaphylaxis is the most common type seen among the Indian population. Aanaphylactic hypersensitivity is the one where the symptoms are seen immediately after exposure to the allergens. In anaphylactic conditions, the antibodies IgE are majorly involved; that is, when an individual is exposed to the allergens for the first time, the allergens get attached to the immune cells especially to the B cells. The allergens trigger the activity of the B cells to transform into plasma cells. Later on, the plasma cells release the antibody IgE. These antibodies are now called as regains which are synthesised only by the allergic individuals.

The reaginic antibodies have a strong affinity towards the mast cells or basophils present in the skin layers. The IgE antibodies get attached to the mast cells through the surface receptors of the mast cells. This state is called as immunised or sensitised for the particular antigen. When an individual is exposed to the same allergen for the second time, it leads to the destructive process of immune cells. The IgE antibody that is attached to the surface of the mast cells now binds to the allergens which result in the cross-link of the IgE antibodies in the mast cells and allergens. This stage leads to the triggering of the cells and a series of enzymatic reactions inside the mast cells. As a result, the mast cells release granules and the process is known as degranulation. These granules contain substances like histamine, serotonin, heparin, etc. which are the primary causative factor for anaphylaxis. Although research on these conditions is advancing to find better solutions for the existing medicines, more insights on the mechanism involved in these hypersensitive conditions should be precisely studied in order to find better and permanent solutions to such allergens in the future medicinal world.
How to cite this article:
Geetha Mahendran. Common hypersensitivity reactions: Anaphylaxis. BioLim O-Media. 25 May, 2016. 4(5).
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