Human blood groups began to be studied back in the late 19th century in the immunology section. Without this knowledge, it would have been impossible to perform a blood transfusion that saved many lives. The doctrine of blood groups is also widely used in surgery, in obstetrics and gynecology, in forensic medicine and in genetics. Knowledge of the distinction between isoantigens is taken into account when transplanting tissues and organs.
Human blood groups are signs of blood that are passed from parents to children. Each has an individual set of group antigens that determine these characteristics. This set of characteristic substances is also called isoantigens.
On their basis, human blood is divided into groups and does not depend on the race to which he belongs, nor on his age, nor on gender. It begins to form at the very beginning of the embryonic period and remains unchanged throughout life. Human blood groups - this is his individual biological feature.
In the practice of physicians, the most significant isoantigens of erythrocytes A and B. The isoantibodies a and ß, sometimes found in human serum, are also taken into account. The simultaneous presence in the blood of isoantigens and isoantibodies of the same type (for example, ß and B) leads to the adhesion of red blood cells and is incompatible with life. Therefore, only heterogeneous substances (for example, A + ß) should be together.
Human blood groups are divided into four, depending on what isoantigens and isoantibodies are present in it. They are indicated by symbols in the form of letters and numbers: - in the first group there are only isoantibodies a and ß - 0aß; - the second group includes isoantigen A and isoantibody ß - Aß; - the third group contains isoantigen B and isoantibody a - Ba; - fourth group contains only isoantigens A and B - AB0.
The compatibility of human blood groups is affected by the presence or absence in the blood of one of the isoantibodies opposing isoantigens in the blood of another. This is taken into account during blood transfusion. Ideal is the use of blood belonging to the same group.
It happens that in addition to the isoantibodies present normally in human blood, isoantibodies from the outside enter it, as a result of which incompatibility of blood groups occurs. This can happen with the transfusion of blood ingredients (plasma, white blood cells, red blood cells), all blood; during pregnancy, when the blood type of the embryo is incompatible with the blood type of the mother; after application of certain vaccines and serums for the purpose of treatment.
After the first month of life in the womb, isoantigens can already be found in red blood cells in the embryo. Their number is growing and reaches a maximum by three years of life. Then its level does not change and only in old age begins to decline. The whole set of isoantigens in the blood does not change during a person’s life. Neither the transferred diseases nor the influence of chemical, biological factors affect its composition.
The determination of the presence or absence of antigens of the Rh - Rh factor system in red blood cells is no less important in medical practice. On this basis, people are conditionally divided into Rh-negative and Rh-positive. It is known that 15% of the population does not contain the Rh factor, while 85% do not. If the expectant mother does not contain the Rh factor, and the fetus inherits the antigen from the father of the Rh positive, then antibodies are formed to it. They affect the red blood cells of the unborn child, causing their destruction (hemolysis).
Human blood groups are determined using standard serums. In erythrocytes, isoantigens are thus found. For example, to determine the 4th blood group, red blood cells and standard serum are placed on a white wetted plate, left at room temperature, and then the agglutination reaction is monitored. With a positive reaction, the isoantibodies of the serum should glue the red blood cells and turn them into tiny red grains. With a negative reaction, any changes are completely absent. In order not to make a mistake, a reaction with two samples is put on each group.