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Blood groups

Blood groups

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The safe supply of blood from a donor to a recipient requires knowledge of blood groups.

We will study two blood group classification systems in the human species: ABO and Rh. In humans there are the following basic blood types in relation to ABO systems: group A, group B, group AB, and group O.

Each person belongs to one of these blood groups. In human red blood cells there may be two types of proteins: agglutinogen A and agglutinogen B. According to the presence or absence of these red blood cells, blood is classified as follows:

  • A group - has only agglutinogen A;
  • Group B - has only agglutinogen B;
  • AB group - has only agglutinogen A and B;
  • Group O - has no agglutinogens.

In human blood plasma there may be two proteins, called agglutinins: anti-A agglutinin and anti-B agglutinin.

If a person has agglutinogen A, they cannot have anti-A agglutinin, just as if they have agglutinogen B, they cannot have anti-B agglutinin. Otherwise, reactions may occur that cause red blood cells to agglutinate or cluster, which can clog blood vessels and compromise blood circulation in the body. This process can lead to death.

In the table below you can check the agglutinogen type and agglutinin type in each blood group:

Blood group Agglutinogen Agglutinin
THE THE anti-B
B B anti-A
AB A and B Don't have
O Don't have anti-A and anti-B

The existence of a substance called Rh factor in the blood is another criterion for blood classification. It is then said that who has this substance in his blood is Rh positive; who does not have it is Rh negative. The Rh factor is named after it was first identified in the blood of a Rhesus monkey.

THE blood transfusion consists of transferring blood from one donor person to another recipient. It is usually performed when someone loses a lot of blood in an accident, surgery or due to certain illnesses.

Blood transfusions need to know whether or not there is compatibility between donor and recipient blood. If there is no such compatibility, there is agglutination of the red cells that begin to dissolve (hemolysis). Regarding the ABO system, donated blood must not contain agglutinogens A; if the recipient's blood has anti-B agglutinins, donated blood may not contain B agglutinogens.

In general individuals Rh negative (Rh-) has no anti-Rh agglutinins. However, if they receive blood Rh positive (Rh+), produce anti-Rh agglutinins.

Because production of these agglutinins occurs relatively slowly, in the first blood transfusion of an Rh donor+ for an Rh receiver-There are usually no major problems. But in a second transfusion, there should be considerable agglutination of the donated red blood cells. The anti-Rh agglutinins produced this time, together with those previously produced, may be sufficient to produce large agglutination in the donated red blood cells, harming the organisms.