The ABO system and the inheritance of the blood group in humans

About what the blood groups are, you should know!

Antigens of the blood system

The antigenic structure of the human body is incredibly complex. Only in blood, modern science discovered about five hundred antigens, combined into 40 antigenic systems: MNSs, AB0, Kell, Duffi, Luteran, Lewis, and others.

Each of the antigens of these systems is genetically encoded and inherited by allelic genes. For simplicity, they are all divided into plasma and cellular. For cellular hematology and transfusiology, cellular antigens (erythro-, thrombotic- and leukocytic) are of great importance, since they possess immunogenicity (the ability to induce an immune response), and therefore, when transfusion is incompatible with cellular antigens of blood, there is a risk of developing hematogenous shock or DIC syndrome with Lethal outcome. Blood antigens consist of two main parts: the antigenic determinant that determines immunogenicity, and the hapten, "weighting" the antigen and determining serological activity.

The first part is highly specific for each antigen, and therefore distinguishes them from each other. So, in system AB0 antigen 0 differs fucose, antigen A-N-ftsetilglyukozamin, and antigen B - galactose. These antibodies are attached to these determinants in the development of the immune response. These antigens are taken into account during blood transfusion, and also when the possible inheritance of the blood group is calculated.

AB0 system and its inheritance

As early as 1901, substances capable of gluing together erythrocytes among themselves, which were called agglutinins (plasma agglutination factors - α and β) and agglutinogens (erythrocyte adhesion factors - A and B) were found in human blood. According to this system, the scientists J.Jansky and K. Landsteiner divided all people into 4 groups, they also calculated the inheritance of blood groups in humans. So, the I blood group has people whose blood contains no agglutinogens, but the plasma contains both agglutinins. Their blood is designated as αβ or 0. People with blood group II have agglutinogen A and agglutinin β (Aβ or A0); people with group III, on the other hand, have agglutinogen B and agglutinin α (Bα or B0), and blood group IV differs in presence of Erythrocytes of both agglutinogens A and B (AB), with no agglutinins. They are determined by a simple laboratory method using special standard sera. Since both agglutinogen are dominant, the inheritance of one of the antigens, i. E. Inheritance of the blood group, is equivalent. The blood group of the unborn child can always be assumed with a probability of 100, 50 or 25% for different combinations of blood groups of the parents. Thus, knowing their antigens, the inheritance of blood groups of children can be traced through the following table.

Equally important is knowledge of the Rh factor, as it is also important for the compatibility of blood groups during transfusion. Thus, Rh-positive blood (Rh +) can be transferred to a patient with Rh-negative blood only once for life and in extreme cases, as the first transfusion will produce Rh-antibodies, which are activated during the second transfusion (and the recipient risks dying From hemotransfusion shock). The same is true for Rh-conflict during conception of the fetus with Rh-positive blood in Rh + mother and Rh-father, so it is so important to expect the inheritance of the blood group of the unborn child.