How Do We Develop Allergies?
Allergens raise a conundrum for scientists in general. These proteins are harmless and can’t damage any cell or tissue in our body. Yet, in allergy sufferers the antibodies in the immune system over-react to these harmless proteins in a harsh way that cause several symptoms like sneezing, coughing and shortness of breath.
For allergy victims the immune system for some reason recognise a perfectly inoffensive antigen, like pollen; as a harmful assailant and gear up the immune defence cells to overproduce allergenic damaging reactions like mild sneezing and coughing or severe, life threatening anaphylactic shock.
The term allergy was introduced in an attempt to describe ‘uncommitted’ biological responses in our body that can lead either to immunity reaction that fight against infection or hypersensitivity reaction that can cause an exaggerated immune response and tissue damage. The immune system provides immediate innate immunity and a delayed specific adaptive immunity.
Innate immunity involves special white blood cells like mast cells, eosinophils, basophils, natural killers and phagocytes, while the adaptive immune cells involve B and T lymphocytes. B cells produce antibodies to neutralise foreign antigens, while T cells, which are divided into two subtypes, cytotoxic T cells and helper T cells, recognise the foreign antigen when it is processed and presented to them by a receptor that is called the major histocompatibility complex (MHC).
The mechanism of the allergic cascade involves IgE production as a consequence to the exposure to an allergen. IgE triggers basophils and mast cells and upon successive exposures to the allergen these cells release inflammatory mediators like histamine that can cause vasodilatation and smooth muscle contraction resulting in inflammation which cause a runny nose, itching, throat swelling, and low blood pressure. At a later stage other immune cells like the eosinophils, platelets and neutophils are also triggered and amplify the allergic cascade.
Allergens were found to possess some common features that may unintentionally stir the immune system like a potent protease activity and structural features that resemble molecular patterns usually found in pathogens. Most scientists however are still uncertain on a common major quality to define a protein as an allergen. Allergy is a coordinated interaction of environment, genetics and molecular factors making it a struggle to define exactly why allergens are allergens
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