The blood volume in an adult is between four to six liters. Blood is composed of red blood cells, white blood cells, platelets, and liquid - plasma. Plasma 90% of water; it also contains proteins, hormones, and other substances. Blood consists of 60% plasma and 40% - from the blood cells. Blood determined based on the blood contained in the antigens and antibodies. Antigens - a protein molecule that are on the surface of red blood cells (RBC) and the antibody contained in the plasma.

The system of blood groups AB0

This system of blood groups - the most famous and widely used today - was discovered by Karl Landsteiner when he was trying to understand why a blood transfusion sometimes helps to save lives, and sometimes leads to death. In 1930, Dr. Landsteiner for his discovery was awarded the Nobel Prize in Physiology or Medicine.

The system identifies four AB0 blood groups:

• Blood group 0 (the first group) - antigens are absent and the plasma has antibodies - agglutinins alpha and beta.
• Blood group A (the second group) - erythrocytes contain antigens or agglutinogens A plasma - beta agglutinins.
• Blood group B (a third party) - agglutinogens The alpha-agglutinin.
• Blood group AB (fourth group) - agglutinogens A and agglutinins absent.

The first group of blood is the most common and most ancient. The fourth group - the "youngest" and most rare.

Blood transfusion inappropriate group may be dangerous to the life of the recipient of the interaction of antibodies and antigens. Since the first group have blood antigens, it can be transfused to the patient from any group in the blood, though this is rarely done - only when there is no blood in the same group as the recipient.

Rh system

Most people on the surface of red blood cells there is an antigen called Rh blood. If a person has such an antigen, his blood is Rh-positive if it is not - Rh-negative. Thus, isolated blood eight groups: each of the four main groups may be Rh + or Rh-. 85% of residents of European countries a positive Rh factor; in Asia and Africa, the percentage of people with a positive Rhesus factor further.

Inheritance of blood groups

If both or just one parent has a positive Rh factor, they can have a child with both negative and positive Rh factor. If both parents are Rh-negative, their child will be the same Rh.

Although blood is 100% dependent on the genes of the parents, the environment in which man lives, can to some extent influence which groups the blood will often be transmitted to future generations (in cases where parents can inherit different blood groups). This is part of the natural selection. It is assumed that this is due to the fact that the same blood in one region may be much more common than in the other.

Other blood group systems

System Diego. Blood groups in this system is determined by the gene SLC4A1. It is responsible for the formation of a protein which transports the ions in the erythrocytes and of them. It is necessary to red blood cells can move carbon dioxide to the lungs, whereupon it safely excreted. Different versions of this protein called Di (a) and Di (b). Non-compliance with this blood group system in transfusion can cause as moderately strong and very serious reactions in the recipient.

In addition, the system Diego is of particular interest to anthropologists as the prevalence of protein Di (a) and Di (b) in different ethnic groups are very different. For example, the protein Di (a) is found mainly in populations of Mongolian origin. It has 36% of the South American Indians, 12% of Japanese and Chinese, and very rare in Caucasians (0.01%) and Africans (as 0.01%). Curiously, the Poles Di (a) is found slightly more often than other Europeans - apparently this is due to the invasion of the Tatars in Poland centuries ago. Di (b) occurs in 99.9% of Europeans and Africans, and more than 90% of Asians.

The system antigens Kell. Kell antigens located on the surface of erythrocytes, and are important in transfusion. If the person does not have the antigen (NCA or K0), and it is transfused donor blood, which has the antigen, with repeated transfusions this can lead to hemolysis. Therefore, people who have no antigen Kell, you can only pour the blood from the same donor, and those who have this antigen fits any blood.

Analysis for blood group

To determine blood type human red blood cells it is mixed with solutions of various antibodies. If, for example, in solution have beta agglyutinyny and erythrocytes - agglutinogens in happen bonding fibers, and the blood of the first group does not interact with agglutinogens A and B. In the laboratory analysis also determined Rh, Kell antigens availability, and etc. All this allows to find the maximum safe blood transfusion.