What is a blood group? In 1900, Landsteiner showed that people could be divided into three groups (now called A, B, and O) on the basis of whether their red cells clumped when mixed with separated sera from other people.

A fourth group (AB) was soon found. This is the origin of the term ‘blood group’. A blood group could be defined as, ‘An inherited character of the red cell surface, detected by a specific alloantibody’.

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Essential Guide to Blood Groups 3rd Edition PDF

Do blood groups have to be present on red cells? This is the usual meaning, though platelet- and neutrophil-specific antigens might also be called blood groups. In this book only red cell surface antigens are considered.Blood groups do not have to be red-cell specific, or even blood-cell specific, and most are also detected on other cell types. Blood groups do have to be detected by a specific antibody: polymorphisms suspected of being present on the red cell surface, but only detected by other means, such as DNA sequencing, are not blood groups. Furthermore, the antibodies must be alloantibodies, implying that some individuals lack the blood group. Blood group antigens may be: •• proteins; •• glycoproteins, with the antibody recognising primarily the polypeptide backbone; •• glycoproteins, with the antibody recognising the carbohydrate moiety; •• glycolipids, with the antibody recognising the carbohydrate portion. Blood group polymorphisms may be as fundamental as representing the presence or absence of the whole macromolecule (e.g. RhD), or as minor as a single amino acid change (e.g. Fya and Fyb) or a single monosaccharide difference (e.g. A and B).
A blood type (also called a blood group) is a classification of blood, based on the presence and absence of antibodies and inherited antigenic substances on the surface of red blood cells (RBCs). These antigens may be proteins, carbohydrates, glycoproteins, or glycolipids, depending on the blood group system. Some of these antigens are also present on the surface of other types of cells of various tissues. Several of these red blood cell surface antigens can stem from one allele (or an alternative version of a gene) and collectively form a blood group system.[1] Blood types are inherited and represent contributions from both parents. A total of 36 human blood group systems and 346 antigens are now recognized by the International Society of Blood Transfusion (ISBT).[2] The two most important blood group systems are ABO and Rh; they determine someone’s blood type (A, B, AB and O, with +, − or null denoting RhD status) for suitability in blood transfusion.

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