Hypersensitivity

Hypersensitivity (dem sanso call hypersensitivity reaction) be an immune response wey be characterized by mechanisms wey dey cause significant tissue damage anaa physiological dysfunction, whether dem direct against pathogens, harmless environmental antigens, anaa self-antigens wey be reproducible upon re-exposure to de antigen. While hypersensitivity mechanisms sam times fi serve protective functions (such as control of infectious diseases), dem be distinguished by dema capacity to cause collateral tissue damage wey fi exceed any protective benefit. Collectively, hypersensitivities be extremely common: hay fever dey affect about 1 insyd 10 people worldwide, asthma dey affect hundreds of millions, den about 1 insyd 12 people get an autoimmune disease.

Insyd 1963, na Philip George Houthem Gell den Robin Coombs introduce a systematic classification of de different types of hypersensitivity based on de types of antigens den immune responses involve. According to dis system, dem know as de Gell and Coombs classification anaa Gell-Coombs's classification, der be four types of hypersensitivity:

 Type I, wich be an Immunoglobulin E (IgE)-mediated immediate reaction.
 Type II, an antibody-mediated reaction canonically wey dey involve IgG, IgM, anaa both.
 Type III, an immune complex-mediated reaction wey dey involve IgG, complement system den phagocytes.
 Type IV, a T cell-mediated, delayed hypersensitivity reaction. 

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Category:Allergology
Category:Effects of external causes
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