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A antigen

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A major type of blood group-ABO antigen characterized by a terminal N-Acetylgalactosamine bound to H antigen; defines blood type A


In humans, blood types are determined by the presence of blood-group antigens, which essentially are of three types: H antigen, A antigen, and B antigen.

The presence of A antigen marks blood type A. Humans with blood type A produce not just the enzyme for H antigen synthesis but also the enzyme (i.e. A-type enzyme) that catalyzes the addition of N-Acetylgalactosamine to a number of H antigen. The number of H-antigen with N-Acetylgalactosamine varies, depending on the subgroup of A antigen genetically expressed in individuals.


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