Different blood groups have a number of distinctive components that can be negatively reflected when two different groups are combined. This phenomenon is explained by the presence on the surface and in the plasma of each individual group of an individual combination of agglutinins and agglutinogens that can distinguish a foreign red blood cell from its own, to prevent its functioning inside the body. Cells with extraneous agglutinogen are perceived as a threat by the human immune system. And for protective purposes, the body seeks to damage and remove them with the help of agglutinins contained in the plasma of its red blood cells.
Even before the beginning of the 20th century, it was believed that any blood could be combined, which was fundamentally wrong. And sometimes everything even ended in deaths, since the transfused blood was not perceived by the body. Bonding and destruction of red blood cells developed. But thanks to K. Landsteiner, who was able to detect and prove the presence of agglutinogens and agglutinins in red blood cells, blood groups are now distinguished, and the blood transfusion scheme has become safe.
Blood types
The system developed by Landsteiner is called ABO. Four blood groups are classified according to it depending on agglutinogens designated A and B and agglutinins a, b in the composition.
Agglutinogens (antigen) - complex substances located on the erythrocyte membrane, are unchanged and inherited from parents.
Agglutinin (antibodies) - immunoglobulins produced in the plasma of red blood cells in a natural way to protect the body from genes that are not on the surface of the red blood cell. They are produced during the first year of life, as a protective function of the immune system upon the ingestion of proteins with foreign antigens.
Blood transfusion chart table| Blood type | Agglutinogen | Agglutinin |
| I group | - | a and b |
| II group | A | b |
| III group | B | a |
| IV group | A and B | - |
As can be seen from the table, each blood group is a difference in the set of antigens and agglutinins that have developed to the missing antigens for protection.
In the plasma of red blood cells, agglutinins of the opposite type are produced from antigens on the membrane. This opposite exists so that when red blood cells enter the body of an extraneous blood group, they are quickly destroyed by antigens, while not harming their own cells.
Rhesus factor
In the scheme of blood transfusion of groups of acceptable combination, it is also necessary to take into account the Rh factor of the blood. The Rhesus factor is a constant characteristic that does not change over the course of life and represents the classification of blood according to the Rhesus system (Rh). The Rh system is based on the identification of six antigens C, D, E, c, d, e on the surface of red blood cells; it was discovered in 1940 by K. Landsteiner and A. Weiner.
If antigen D is found on the surface of red blood cells (found in 80% of people) or the simultaneous presence of C and E antigens, then the blood belongs to a positive Rh factor, designated Rh +. If antigens of this group are not found, then the Rh factor will be negative Rh-.
Rh factor significance during transfusion
For transfusion, blood having the same values according to the Rhesus system is allowed. So, a recipient with a negative Rh factor is suitable only for donated blood of a negative indicator. The same is with positive, but in critical cases, infusion of blood with a negative Rh factor in small quantities, a maximum of 200 ml, is allowed. With this transfusion, incompatibility does not occur, but when red blood cells with a negative Rh factor are erythrocytes with a positive value, a protective reaction of the immune system to antigen D is observed. When foreign red blood cells are detected, the immune system begins to produce agglutinins (d, c, e), which damage red blood cells, which entails serious consequences for the recipient's body. According to the Rhesus system and ABO, eight types of blood are distinguished.
Blood compatibility
Blood transfusion is a blood transfusion procedure that is used to restore blood balance and blood circulation. Donor blood must be compatible across both recipient blood systems. For a long time it was believed that there is a universal donor and a universal recipient. At the moment, both of these concepts are already practically extracted from the medical system. However, in critical situations, in the absence of time and donor blood of an identical group and Rh factor, it is sometimes still used in transfusions of small volumes, not more than 500 ml.
The universal donor includes blood of the first group and a negative rhesus value 0 (I) Rh-, since it does not have its own antigens. A universal recipient is the fourth positive group AB (IV) Rh +, due to the presence of antigens A and B. on the erythrocyte membrane. However, they try to transfusion with identical groups.
I blood group: compatibility scheme
During transfusion, a group with a negative rhesus value (0 (I) Rh-) can be a donor for all blood groups with a positive and negative Rh factor during emergency transfusion and, if a large volume is necessary, act as a donor for group I with an identical rhesus index.
For a recipient with a first blood group and a positive Rh factor, donated blood may be the first positive or negative group 0 (I) Rh - / +. In the first blood group with a negative rhesus index, transfusion is carried out only with the identical group 0 (I) Rh-.
Second group compatibility
The second negative group A (II) Rh- can become a donor for the second and fourth with any rhesus index. The second positive group A (II) Rh + is used as a donor only for the second and fourth AB (IV) Rh + with a positive Rh factor.
A recipient with a second positive group A (II) Rh + can receive blood from the first 0 (I) Rh - / + and the second group A (II) Rh - / + with any rhesus index. If the recipient's blood is indicated by a negative Rhesus A (II) Rh-value, transfusion is performed with groups, as for the second positive, only extremely negative Rh factor.
Third Group Compatibility
As a donor third blood group with positive Rh factor B (III) Rh +
used for transfusion to recipients with the third and fourth group with a positive rhesus index. The third negative group is compatible for donation with the third and fourth blood groups, at any value of the Rh factor in the recipient.
Owners of the third positive group receive transfused donor blood of the first and third groups with negative or positive Rhesus. The third negative is characterized by compatibility with the third and fourth group with a negative Rh factor.
Fourth group compatibility
Donor blood of the fourth group with a positive Rh factor is suitable only for transfusion to recipients with an identical group and rhesus index. The fourth negative is compatible for transfusion also only to the fourth group with negative and positive Rhesus.
But the recipient with the fourth positive group AB (IV) Rh + is universal and perceives with a positive Rhesus value absolutely all blood groups with any Rhesus values. In case of a negative Rhesus factor, transfusion uses donor red blood cells of all groups with only a negative Rhesus index.
Risks of transfusion of incompatible groups
The main risk for blood transfusion is agglutination.
Agglutination - the process of gluing red blood cells, which leads to their destruction, develops when blood enters the body with agglutinogen, to which the recipient's blood has developed agglutinin. This means that agglutination occurs when blood is combined with antigens of the same name and agglutinins A and a, B and b. With this combination, antibodies (a or b) developed for the missing antigen (A or B) destroy donor red blood cells, resulting in their sedimentation and subsequent hemolysis (decay).
Blood is the main transporter of oxygen to all cells of the body, therefore blood transfusion shock forms after the breakdown of red blood cells, which can cause serious consequences and even death. It is on the basis of such risks that much attention is paid during blood transfusion to schemes of blood groups compatible with each other.
The system of ABO and Rhesus is the main one in the classification, but not the only one. On the surface of the erythrocyte membrane there are many other antigens that are currently involved in the selection of compatible donor blood. But, more and more private clinics additionally determine the presence or absence of a rare Kell antigen, with a positive value of which donor red blood cells are incompatible with any others.