Blood Types: Classification Systems, Transfusion Compatibility

Blood is a very important biological fluid that is involved in gas exchange (transportation of oxygen to cells and carbon dioxide to the lungs), and also protects against various biological threats (bacteria, viruses, fungi).

A patient may need a blood transfusion if they have lost blood due to illness, injury, or injury.

In the composition of the blood: plasma and cells (platelets, leukocytes, erythrocytes). Erythrocytes are considered the main carriers of antigens.

Antigens help the body fight foreign bodies by creating characteristic antibodies.

In the case of an incorrect choice of a donor for a blood recipient, an ineffective transfusion may occur. Erythrocytes from the donor's blood can be associated with the recipient's erythrocyte antigens as foreign bodies. The resulting antibodies can destroy "foreign" erythrocytes. But there may be a reverse case, antibodies from the donor's blood (wrong blood type) can attack the patient's red blood cells.

In order to choose the right donor, a compatibility analysis is done. Only erythrocytes have about 20 antigens. Based on the similarity of antigens, blood is classified into similar groups.

The main blood classifications are the AB0 system and the Rhesus system.

Karl Landsteiner, who discovered the A and B antigens back in 1900, is considered the pioneer of the AB0 blood group systems. For this discovery in 1930 he received the Nobel Prize.

He noticed that the second (A (II)) and fourth (AB (IV)) blood groups have antigen A, and the third (B (III)) and fourth (AB (IV)) blood groups have antigen B.

At the same time, the third (B (III)) and first (0 (I)) groups have anti-A antibodies, and the second (A (II)) and first (0 (I)) groups have anti-A antibodies. AT.

Theoretically, the first (0 (I)) group is a universal donor, that is, people with this group can donate blood to people with other blood types, but the fourth (IV (AB)) group can receive blood from all other blood types.

In practice, and only in extreme cases, blood transfusion from one blood type to another blood type is possible only within 500 ml, and it is best to avoid such procedures!

In medical practice, blood transfusion preferably occurs from donors to patients with the same blood type! Thus, less blood is inactivated during transfusion.

The Rhesus system refers to additional antigens E, e, C, c and D (D). The presence of the D antigen on the surface of red blood cells refers the patient to Rh + (positive Rh), but the absence of this antigen - to Rh- (negative Rh).

The Rhesus system was discovered by the same Karl Landsteiner in 1940 while studying Rhesus Macaques from Southeast Asia, for which he received the posthumous Lasker Prize in 1946 (he died of angina pectoris in 1943).