Donated blood will help the patient only if it is compatible with him, and there are actually not four types of blood - there are many more. Why has medicine abandoned the concept of "universal donor", what is the Rh factor and how is transfusion done now?
“It is impossible to say exactly how many types of blood. There are a lot of them, I would even say that each person has his own type, everything is so individual. But there are clinically significant classifications: according to blood group, Rh factor and some other antigens,”Emin Salimov, a transfusion doctor, tells RIA Novosti.
He heads the department of the Blood Center of the First Moscow State Medical University. Sechenov, where about seven tons of human blood are collected annually for two dozen university clinics. Donated blood, before entering the patient's body and saving his life, will pass through several laboratories, where it is typed by antigens, tested for infections, divided into components - erythrocytes, platelets and plasma - and kept in quarantine for some time.
The risks of unpleasant complications will be minimized as much as possible. But all the same, in the hospital, immediately before the transfusion, the transfusion doctor will again test the components of the donated blood for compatibility with the recipient - those who receive it.
Ambiguous red blood cells
In the 17th century, scientists tried to transfuse the blood of lambs and calves into the insane in the hope that this would cure them of mental ailments. For patients, this usually ended badly - they died.
In the 19th century, British physician James Blundell decided that only human blood should be given to people. But he did not know about different types of blood, and more than half of his patients died in agony.
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Red blood cells - erythrocytes - were to blame for this. When transfused, they can clump together and turn into clots that disrupt circulation, cause profuse bleeding, make breathing difficult, and the person dies. And they can function normally, delivering oxygen to the tissues of the body.
“An erythrocyte is a cell that is slightly concave inward. In textbooks, it is usually drawn smooth, but it is not. The outer cell membrane is covered with many genetically predetermined molecular compounds. In particular, among them there are special proteins - antigens A and B. If you received a blood transfusion and the newcomers and your erythrocytes have the same antigen, then everything will be fine. If the antigens are different, then the body recognizes other people's erythrocytes and starts attacking them,”explains Tatiana Bugakova, transfusion physician.
The AB0 blood group system. The blood group is determined by the type of antigen that is present on the surface of erythrocytes / Illustration by RIA Novosti / Alina Polyanina.
Red blood cells, when hit by antibodies, clump together and precipitate in lumps. For the first time such a strange reaction of erythrocytes to the serum of someone else's blood was observed in 1900 by the Austrian immunologist Karl Landsteiner. On the basis of the data obtained, he divided the blood into three groups: 0 (I), or the first, - there are no antigens A and B on the surface of erythrocytes; A (II), or the second, - antigen A is present; In (III), or the third, there is antigen B. For this discovery, the scientist was awarded the Nobel Prize in Physiology or Medicine in 1930.
The fourth blood group AB (IV) - when both types of antigens are present on the outer cell membrane of erythrocytes - was described in 1902 by Alfred Decastello and Adriano Sturli.
Are you positive or negative
The way Landsteiner determined different blood types at the beginning of the 20th century is still used today. In the blood test room, a nurse takes samples from my finger.
“After the injection, the first drop must be removed. It contains interstitial fluid, which can distort the result,”she explains.
Test for determining the blood group according to the AB0 system / RIA Novosti / Alfiya Enikeeva.
The nurse distributes the blood drops into the four indentations of a small white plate. There is also added tsoliclon - a saline solution of monoclonal antibodies to antigens located on the surface of erythrocytes. The folded red blood cells show that I have a rare fourth positive group.
Positive or negative - this depends on whether there is antigen D on the surface of the red blood cells, better known as the Rh factor. It was also discovered by Landsteiner in experiments on rhesus monkeys. Hence the name.
If a patient with a negative Rh factor is transfused with "positive" blood, red blood cells clump together, blood circulation will be impaired, and the person may die. True, the body will not start attacking other people's blood cells immediately. It takes time to develop antibodies to the Rh factor, so compatibility problems often arise with repeated transfusions.
Kell factor
“You see, the Rh factor and group antigens already produce eight different types of blood. But a dozen more antigens are immunologically significant for transfusilology (the science of blood transfusion),”says Emin Salimov.
One of them is the Kell antigen (K), named after the first patient in whom it was discovered in the 1950s. It occurs in every tenth person. Transfusion of erythrocytes from a Kell-positive person to a Kell-negative person is just as dangerous as if the Rh factor does not match.
“Today, screening for Kell antigen is performed on all blood donors, and if it is detected, red blood cells can only be transfused into a Kell-positive recipient. When transfusing plasma, platelet and leukocyte concentrates, Kell antigen is not taken into account. No erythrocytes, no antigen,”the doctor explains.
Everyone has their own donor
The blood obtained from the donor is separated in a centrifuge into fractions, or layers - platelets, erythrocytes and plasma. This avoids a massive immune response during transfusion and, as a result, serious problems.
Chief Physician of the Blood Center of the First Moscow State Medical University. Sechenova Emin Salimov shows centrifuges in which whole blood is separated into fractions / RIA Novosti / Alfiya Enikeeva.
“There used to be the concept of a 'universal donor' - blood of the first negative group suits everyone. Today, there is only group transfusion and testing for infections and compatibility for some antigens,”Tatiana Bugakova emphasizes.
“We only test for clinically relevant antigens. In general, there are a lot of them: more than 250 antigens of blood groups are known, united in 25 systems. Most often, antigens are found on erythrocytes,”says Salimov.
Why are there so many antigens
Most of these antigens, when transfused, do not cause a conflict between donor blood cells and the recipient's body. Some of them are very similar to receptors (Cromer system). Others are more structurally concerned. For example, glycophorin proteins (MNS system) are responsible for the formation of a negative charge on the surface of an erythrocyte. Electrostatic repulsion prevents the spontaneous clumping of red blood cells.
Some antigens do humans a disservice. For example, the malaria parasites Plasmodium knowlesi and Plasmodium vivax use the Fya and Fyb antigens (Duffy system) to attach to the red blood cell and enter the cell. The inhabitants of West Africa do not have these antigens, and thus they are protected from a dangerous disease. Europeans, having arrived in Africa, due to the presence of Fya and Fyb, run the risk of contracting this infection.
However, despite the proven relationship of some diseases and blood groups, more precisely, the antigens associated with them, scientists agree: the hypothesis of the emergence of blood groups due to the close proximity of a person to infectious agents has not yet been confirmed.
Alfiya Enikeeva
