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Hypersensitivity
Hypersensitivity (also called hypersensitivity reaction or intolerance) is an abnormal physiological condition in which there is an undesirable and adverse immune response to an antigen. It is an abnormality in the immune system that causes Immune disorder, immune diseases including allergies and autoimmunity. It is caused by many types of particles and substances from the external environment or from within the body that are recognized by the immune cells as antigens. The immune reactions are usually referred to as an over-reaction of the immune system and they are often damaging and uncomfortable. In 1963, Philip George Houthem Gell and Robin Coombs introduced a systematic classification of the different types of hypersensitivity based on the types of antigens and immune responses involved. According to this system, known as the #Gell and Coombs classification, Gell and Coombs classification or Gell-Coombs's classification, there are four types of hypersensitivity, namely: Typ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Type I Hypersensitivity
Type I hypersensitivity (or immediate hypersensitivity), in the Hypersensitivity, Gell and Coombs classification of allergic reactions, is an allergic reaction provoked by re-exposure to a specific type of antigen referred to as an allergen. Type I is distinct from Type II hypersensitivity, type II, Type III hypersensitivity, type III and Type IV hypersensitivity, type IV hypersensitivities. The relevance of the Gell and Coombs classification of allergic reactions has been questioned in the modern-day understanding of allergy, and it has limited utility in clinical practice. Exposure may be by ingestion, inhalation, injection (medicine), injection, or direct contact. Pathophysiology In type I hypersensitivity, B cell, B cells are stimulated (by T helper cell#Th1/Th2 model, CD4+ Th2 cells) to produce IgE antibodies specific to an antigen. The difference between a normal infectious immune response and a type 1 hypersensitivity response is that in type 1 hypersensitivity, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |