blood-group



blood-group defined in 1951 year

blood-group - blood-group;
blood-group - Group of people bearing the same antigens on their red blood cells. There are four main groups, whose blood cannot be mixed without clumping of their red blood cells; they are A, B, AB and O. Clumping (agglutination) occurs when blood from any two different groups is mixed, owing to a reaction between substances (agglutinogens) on red blood cells, and other substances (agglutinins) in plasma. Group A has agglutinogen A on its cells and agglutin anti-B (which reacts with agglutinogen B) in its plasma. Group B has agglutinogen B and agglutinin anti-A (which reacts with agglutinogen A). Group AB has both agglutinogens but neither agglutinin. Group O has neither agglutinogen but both agglutinins. Possession of agglutinins is not due to acquired immunity; every individual has the agglutinins which react with the agglutinogens he has not got. The four groups are due to different combinations of three multiple allelomorphs, g, IA, IB; g is recessive to the other two, which show no dominance to each other. Homo-zygous g is group O, homozygous IA or heterozygous IAg are group A; homozygous P or heterozygous IBg are group B; heterozygous IAP is AB. Proportions of the four groups within population are very different in different parts of the world. From point of view of blood transfusion, introduction of corpuscles containing agglutinogen for which recipient has agglutinin must be avoided. The converse is not so important. Members of the population differ in other antigens carried on red blood cells (e.g. M and N antigens, forming M, MN, and N types); but since agglutinins for these are not normally present in plasma, they have not the same significance in transfusion, though immunity to them may be acquired by repeated transfusion. See also: Rh factor. Similar blood groups occur in other Primates.

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