Question

Allergies are an overreaction of the immune system towards non-pathogen allergens. Describe the antibodies, cell types, and other proteins involved in both the early and late allergic response. Then describe how this response would typically be used in a typical immune reaponse.

Answer 1

An allergic reaction occurs when the immune system overreacts to a harmless substance known as an allergen. The immune system controls how your body defends itself. For example, if you have an allergy to pollen, your immune system identifies pollen as an invader or allergen. Your immune system overreacts by producing antibodies called Immunoglobulin E (IgE). These antibodies travel to cells that release chemicals, causing an allergic reaction. This reaction usually causes symptoms in the nose, lungs, throat, sinuses, ears, etc, each type of IgE reacts specifically for each type of allergen. There are several types of allergic disease, for eg, Conjunctivitis, or eye allergy, occurs when the eyes react to allergens with symptoms of reddening, itching and swelling, eczema, often results from an allergen being exposed to your skin symptoms include itching, reddening and flaking or peeling of the skin, If you have a food allergy, your immune system overreacts to a particular protein found in that food. A single allergen exposure produces an acute reaction, which is known as an early-phase reaction or a type I immediate hypersensitivity reaction. which could be followed by a late-phase reaction. With persistent or repetitive exposure to allergen, chronic allergic inflammation develops.

Early phase allergy reaction : This occurs within minutes of exposure to an antigen or allergin, this is a  IgE-mediated type I immediate hypersensitivity reaction, reaction can be local or systemic,  In such reactions, IgE bound on mast cells and basophils and is crosslinked by allergen, resulting in the release of the cells and mediators. These events cause vasodilation, increased vascular permeability with oedema, and acute functional changes in affected organs Some of the released mediators also promote the local recruitment and activation of leukocytes, contributing to the development of late-phase reactions.These can bronchoconstriction, airway mucus secretion, urticaria, vomiting and diarhoea.

Late phase allergy reaction,these reactions develop after 2 to 4 hours of exposure to an allergin, mediators that initiate late-phase reactions are thought to be derived from resident mast cells activated by IgE and allergen or from T cells that recognize allergen-derived peptides.In the lungs,they cause oedema, pain, warmth and redness of skin these reactions are characterized by airway narrowing and mucus hypersecretion leading to asthma like symptoms.

Chronic allergic reaction, in which persistent inflammation induced by prolonged or repetitive exposure to specific allergens, typically characterized not only by the presence of large numbers of innate and adaptive immune cell and also changes in extracellular matrix and change in structural cells of affectd tissue.