Blood groups. Blood group determination

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Blood groups are signs of blood being passed down from generation to generation. Based on these characteristics, the blood of all people (regardless of race, age and sex) is divided into groups. A person's affiliation to a particular blood group is an individual biological feature of him (it begins to take shape during development in the mother's womb and does not change for the rest of his life).

Isoantigens in erythrocytes (red blood cells) - isoantigen A and isoantigen B, as well as isoantibodies - isoantitelo a and isoantitelo v, which are normally present in the serum of some people, are many practical factors. Human blood contains only different isoantigens and isoantibodies (e.g., A + v and B + a) because if isoantigens and isoantibodies of the same sign (e.g., A and a) meet, the erythrocytes stick together and the person dies.

Depending on the presence of isoantigens A and B in human blood, as well as isoantibodies a and b, they can be divided into four groups, conditionally expressed in letters and numbers:

• 0 a v (I) - blood group with only, a, v isoantibodies;

• A v (II) - a blood group containing the isoantigen A and the isoantibody v;

• B a (III) is a blood group that contains the B isoantigen and the isoantibodies a.

• AB0 (IV) is a blood group that contains only A and B isoantigens.

The doctrine of blood type originated in the late nineteenth century. It is an important part of general immunology. The science of blood type is widely applied in almost all fields of medicine. Blood group studies showed that isoantigen A did not have the same marker. Isoantigen B differs in that it has more of the same character than isoantigen A. In addition, specific antigens such as H and 0 were found in the erythrocytes of some people. In the AVO system, the Rh system of the blood group (Rhesus-Rhesus) is one of the most complex systems of the blood group, consisting of more than 20 isoantigens. The presence of the Rh system antigen Rh factor in the erythrocytes of 25% of people was found to be absent in 15% of people. Depending on the presence or absence of this factor, people are conditionally divided into two groups - rhesus-positive and rhesus-negative. In the absence of Rh-factor in the blood of the mother, the developing fetal rhesus factor produces antibodies against it under the influence of a positive paternal antigen, which, in turn, affects the fetal erythrocytes and their hemolysis (dissolution). )resulting in. Thus, hemolytic anemia manifests itself in the form of rhesus-conflict (conflict), which sometimes leads to death. Rhesus-conflict can also occur when Rhesus-positive blood is transfused into Rhesus-negative people.

In addition to isoantigens in erythrocytes, other components of the blood are found to contain only their own isoantigens. Thus, the presence of leukocyte groups combining more than 40 antigens of leukocytes was revealed. Although isoantigens belonging to other systems of human blood are of less practical importance than AB0 and Rh systems, they are of great importance for the fields of forensic medicine, genetics, anthropology.

Blood group-specific traits are determined by genetic factors, i.e., the antigenic properties of children’s blood depend on the parent’s blood type. This allows forensic medicine to address complex issues such as identifying a child’s parents.

Determination of blood groups. Blood groups are determined at room temperature 15-20 ° C. To determine the blood group, a new blood serum obtained from two different series from each of the three groups examined is required. A clean white porcelain plate is taken and the edges of its first three groups are marked with a special pencil as 0 (I), A (II), B (III). The corresponding group sera in two different categories are placed side by side on these marks and dropped two drops on a plate. After the drops have been dropped, each dropper is placed back into the one from which the whey vial was taken. Three small drops of blood, the group of which must be determined, are drawn into the serum with separate glass rods (the ratio of blood to serum is 10: 1 or 15: 1).

Shake the plate continuously, mix well and observe for 4 minutes. Then 1 drop of saline solution is added to the drops of the agglutination mixture (to eliminate false agglutination), it is mixed and examined: if the test blood is group 0 (I), not a single drop has agglutination; if the blood belongs to group A (II), agglutination occurs with sera of groups 0 (I) and B (III) without agglutination with serum of a nominal group. Group B (III) blood does not agglutinate with group one, but agglutinates with group 0 (I) and A (II) sera.

If the blood being tested belongs to group AB (IV), agglutination will occur with all the serums obtained to determine the blood group. It will be necessary to verify additional control with standard serum belonging to group AB (IV). The absence of agglutination with this serum allows the blood to be considered to belong to group AB (IV).