Human Anatomy and Physiology - I. V. Gayvoronsky 2011

Internal Environments of the Body. Blood
Blood Groups

Even in ancient times, it was observed that severe Blood loss from wounds led to the rapid death of the injured. However, almost all early attempts to transfuse blood from a healthy person to a patient were doomed to failure. It was only at the beginning of the 20th century, following the discovery of blood groups by the Austrian scientist K. Landsteiner, that the transfusion of this liquid tissue became possible.

Human erythrocytes have specific Proteins on their membrane surface called agglutinogens, which act as specific markers—Antigens. Special Antibodies, known as agglutinins, constantly circulate in human blood serum.

Currently, a fairly large number of blood group systems are known. However, the two main ones are the ABO system and the rhesus (Rh) factor. A person's blood group remains unchanged throughout their life.

The ABO System. Two varieties of agglutinogen proteins are located on erythrocytes: one is designated as A, and the other as B. Meanwhile, the serum contains either a (alpha) or ß (beta) agglutinins. In any given individual, agglutinogens and agglutinins cannot be of the same type. When foreign red Blood Cells enter the body and their marker proteins match the antibodies in name (A — a; B — P), agglutination occurs—the clumping and destruction of erythrocytes. Hemoglobin is released from the destroyed red blood cells into the plasma. This process is called hemolysis. Consequently, most early attempts at blood transfusion prior to K. Landsteiner's discovery were unsuccessful, because the agglutination reaction evolved as a protective mechanism aimed at preserving the individual antigenic integrity of the Organism.

According to the ABO system, there are four blood groups. Individuals with the first blood group — O(I) — have neither A nor B agglutinogens on their Erythrocyte membranes, while their Blood Plasma contains both a and ß agglutinins.

The second blood group is characterized by the presence of agglutinogen A on the erythrocytes, with ß-agglutinins circulating in the serum. The designation for this blood group is A(II). People with the B(III) group have B-agglutinogens on their erythrocytes and a-agglutinins in their serum. Individuals with the fourth blood group, AB(IV), have both A and B agglutinogens On the surface of their erythrocytes, and their serum lacks agglutinins (Table 13.2).

It has been established that people with the first blood group account for 34%, the second blood group occurs in 38%, the third group in 20%, and the fourth is much rarer, at 8%.

Rhesus Factor. This is another marker protein. In 85% of people, it is present on The surface of erythrocytes, making their blood rhesus-positive (Rh+). The remaining individuals lack the rhesus factor, meaning their blood is rhesus-negative (Rh^-).

Under normal conditions, rhesus-negative individuals do not produce antibodies against this marker protein. These antibodies appear only when erythrocytes bearing the rhesus factor on their surface enter the body. It should be noted that The production of anti-rhesus antibodies is quite slow. Therefore, the greatest danger is posed by repeated contact with rhesus-positive blood. All of this is accompanied by agglutination, just like in blood transfusions incompatible by the ABO system. Such a scenario can occur in the following cases:

1) repeated transfusion of rhesus-positive blood to a rhesus-negative recipient;

2) The Development of rhesus incompatibility (Rh incompatibility) during the Pregnancy of a rhesus-negative woman carrying a rhesus-positive fetus (inheriting this factor from the father); while the first pregnancy may proceed normally, the INTRAUTERINE DEVELOPMENT OF a second child can lead to complications because the mother's body produces anti-rhesus antibodies against the fetal erythrocytes. These antibodies enter the fetus's body, causing hemolysis, which can result in the death of the child or the development of intrauterine pathology (hemolytic disease of the newborn).

Class="center">Table 13.2 ABO blood groups

Currently, with early Diagnosis of this condition, a series of measures are carried out to prevent hemolysis and preclude any developmental abnormalities in the fetus.