Rhesus, rhesus factor, blood groups
English: rhesus factor
The Rhesus factor, like the AB0 blood group system, is a classification of blood groups determined by proteins on the surface of red blood cells (erythrocytes).
As on all cells, red blood cells contain a large number of protein molecules against which the body's immune responses can be directed. Five different proteins are called the rhesus factor: C, c, D, E and e (as a continuation of blood groups A and B).
C and c, as well as E and e are different protein molecules, whereas d only describes the absence of D. Depending on the hereditary disposition, different combinations of these proteins (which, since they can also be the target of a defense reaction by antibodies, are also referred to as antigens) can come about.
Inheritance takes place in a similar way to the AB0 system. Each person receives a variant C (C or c), D (D or no D, which is referred to as d) and E (E or e), which together determine the Rhesus blood group.
Since the complex notation, for example CcDDee (from one parent C, from the other c, from both D and e) is not always necessary in everyday clinical practice, and factor D is the most important, one often limits oneself to the simplification Rhesus-positive (Rh (D) +, Rh + or Rh) or Rhesus-negativlut (Rh (D) -, Rh- or rh), each of which only describes the presence or absence of factor D. A person who has inherited the factor D from at least one parent (e.g. CcDdee or CCDDEE) is called rhesus-positive. Only those who have not inherited factor D from any parent (e.g. CCddEe) are rhesus negative.
The rhesus system was put together in 1937 by the Austrian Karl Landsteiner and the American Alexander Solomon Wiener discovered. Landsteiner had that as early as 1901 AB0 system discovered and received the Nobel Prize in Medicine for it in 1930. Since they succeeded in discovering the blood group characteristics during research on rhesus monkeys, the name rhesus system or "Rhesus factor"For the factor D.
In Germany and Central Europe, around 83% of the population are Rhesus-positive, which can lead to shortages of suitable transfusion blood for Rhesus-negative recipients of blood donations. The situation for rhesus-negatives is even more critical in Eastern Europe, where they sometimes make up only 4% of the population.
The main importance of the rhesus system lies in the classification of blood transfusions and in the dangerous Haemolyticus neonatorum disease, a disease of the unborn child in which the mother makes antibodies against the blood of the fetus.
The Rhesus system occupies a similar position in the classification of blood for transfusions as the AB0 system. This should ensure that a Rhesus negative does not receive Rhesus positive blood, otherwise complications can arise. The formation of antibodies against the Rhesus D protein, which can damage the embryo during pregnancy, is also important. Conversely, a rhesus positive has nothing to fear if he is transfused with rhesus negative blood, since there is no rhesus factor on the donated blood cells against which he could form antibodies.
Of the Haemolyticus neonatorum disease can arise when a rhesus negative mother who has raised antibodies against rhesus factor is pregnant with a rhesus positive child. Due to the inheritance already mentioned, it can happen that a child from a rhesus-negative mother becomes rhesus-positive itself through a rhesus-positive father. When a Rh-positive child is born, sufficient amounts of the child's blood can enter the mother's circulation to build up an immune reaction (similar to a vaccination) against the Rh factor. Theoretically, it is also possible to build up rhesus immunity by giving the mother a rhesus-positive blood supply, which is why very strict requirements apply here. In the case of a pregnancy with a rhesus-positive child, the mother's newly formed antibodies now find their way into the child's circulation. There they lead to the dissolution of the embryo's red blood cells and can seriously damage it. As a precautionary measure, a mother can be given medication for the first birth of a Rh-positive child that prevents the build-up of immunity against the Rh factor.