People differ from each other by blood type in the same way as hair color. Which group your blood belongs to depends on which proteins are on the membrane of your red blood cells and which proteins are in the blood plasma (this is a liquid located in the blood vessels in which red blood cells are weighed).

Proteins in red blood cells are called agglutinogens, and plasma proteins are called agglutinins. Agglutinogens are of two types: A and B. Agglutinins are also of two types: a and c. Do not worry, they are indicated in small letters to avoid confusion.

Blood Classification

This is how this system works. Suppose Emily’s blood type is A. This means that her red blood cells contain agglutinogen A, and her blood plasma contains agglutinin B. Lily has blood of group B. This means that her red blood cells contain agglutinogen B, and agglutinin a in the blood plasma. Jeff has a blood type AB.

Interesting fact: people with blood type 0 are called universal donors - they can give blood to any person with any blood type.

This means that its red blood cells contain agglutinogens A and B, but there are no agglutinins in the plasma at all - neither a nor b. Juan’s blood type is O. This means that there are no agglutinogens in his red blood cells — neither A nor B, but the plasma contains agglutinins — a and e.

Why are some blood types not compatible?

Your body considers blood agglutinogens different from yours as uninvited aliens.If Emily with her blood group A transfuses the blood of group B, then the agglutinins contained in her plasma attack red blood cells with agglutinogens B, as a result, these cells stick together and block blood flow in the vessels of the internal organs, for example, the vessels of the brain, which will threaten Emily's life. Similarly, patients with blood group B must not be transfused with blood of group A, patients with group O must not be transfused with blood of either group A or group B. To avoid a possible mistake, before each blood transfusion the patient is checked for her group.

Universal donors

No blood group reacts with group O. You remember that in the red blood cells of this group there are no agglutinogens that can attack agglutinins. Therefore, people with blood type O are called universal donors - they can give blood to any person with any blood type. Since the blood of group AB has agglutinogens A and B, people with such a group can transfuse blood of any group, since there are no called blood agglutinins in the blood of AB, which can attack red blood cells of donors. People with blood type AB are universal recipients.

Rhesus blood factor

Blood in which there is no Rh factor is called Rh negative (Rh-), and only Rh negative blood can be transfused with people with such blood. Otherwise, antibodies appear in the Rh blood of a negative person, which rejects Rh positive blood during repeated transfusions.

Interesting fact: red blood cells in many people contain a protein called the Rhesus factor, their blood is called Rh - positive (Rh +).

Blood group distribution

You inherit a blood group, like a hair color, from your parents, and blood groups with different frequencies are found in different nations, and you can judge by blood groups where the ancestors of a person came from. Throughout the world, people for one reason or another determine the blood group, so scientists were able to establish how blood groups are distributed on Earth among different peoples.

In the United States, blood type A was found in 41 percent of whites, and only in 27 percent of African Americans. Almost all Indians of Peru have blood type O. In Central Asia, the most common blood type is B.

Why do people differ in blood types? This is not entirely clear. However, scientists have found a relationship between blood types and certain diseases.

The relationship of blood groups and diseases

For example, people with blood type O are more likely than others to suffer from a stomach ulcer, people with blood type A are more likely to suffer from stomach cancer. A very strange fact is that proteins similar to the agglutinogens of human blood groups are found on the surface of some bacteria and viruses.

If a microbe penetrates into your body, the proteins of which are similar to the proteins of the cells of your blood, then the immune system may fall into error and mistake the aggressor for its own and let the infection pass freely into the body. Here is an example. The surface of the bacterium that causes bubonic plague is similar in composition to the red blood cells of group O.Therefore, scientists suggest that people with blood type O are especially sensitive to such bacteria and are more likely to get bubonic plague.

Interesting fact: if you have blood type 0, then your body can take the bubonic plague sticks for completely friendly cells.

Bubonic plague

Scientists think that the epidemic of bubonic plague began in Southeast Asia and spread to the West. Having reached Europe, the plague killed a quarter of the population there in the 14th century; this epidemic in Europe was called the Black Death. In Central Asia, where plague is common for a very long time, the population has almost no blood type O. This shows that group O was a major disadvantage in surviving under the constant threat of the plague. And those who had groups A, B and AB had obvious advantages when they encountered a plague stick. Scientists hope that elucidation of the connections between blood groups and the diseases to which their carriers are exposed will someday explain the origin and consolidation of blood groups among human populations.

Blood group designation terminology in Russia

A note must be made in connection with blood types. In Russia, a slightly different terminology has traditionally been adopted to indicate the group membership of blood: group O is called the first, group A is the second, group B is the third, group AB is the fourth. Everything else can be accepted without change.

And one more remark, since the diversity of blood groups is not limited to the four named and with blood transfusion of even one group, numerous complications can occur, then by order of the Ministry of Health it is strictly forbidden to transfuse patients with blood of other groups or not matching the Rh factor. Therefore, the concepts of “universal donor” and “universal recipient” have historical significance.