Rh and MN System

Rh blood system

Experiments developed by Landsteiner and Wiener, in 1940, showed that blood is classified into groups (positive and negative) by the presence or absence of an antigen on the surface of the red blood cell that was first found, performing experiments on the monkey of the genus “Rhesus” , giving the name of Rh factor.

The conclusions obtained from then on would lead to the discovery of a membrane antigen that was called Rh (Rhesus), which existed in this species and not in other guinea pigs and, therefore, stimulated the production of antibodies, called anti-Rh.

Rh – (negative) blood does not have this antigen on the surface, and Rh + (positive) does.

In the human species, we find several types of blood systems, which can be observed in other species, mainly of superior monkeys.

Photo: Reproduction

MN blood system

The Mn blood system occurs in humans and involves the presence of M and / or N antigens in red blood cells, however several people have both antigens.

It was concluded that there were three groups in this system: M, N and MN.

M and N are the alleles adopted in this system, which can be M or N, since there is no dominance or recessivity (codominant inheritance).

Genotype types: MM, NN or MN

Donations in this system are free, anyone can donate blood to anyone else. Thus, the MN system does not present problems in transfusions because the antigen-antibody relationship is very weak, with no considerable agglutination. The production of anti-M or anti-N antibodies occurs only after sensitization.

Fetal erythroblastosis or hemolytic disease of the newborn

It is a disease characterized by the destruction of red blood cells of the fetus or newborn, which can lead to death. This problem occurs when the mother is Rh – and her blood comes in contact with the baby’s blood, which has Rh +. However, how does this happen?

It occurs during pregnancy, through the placenta, when the mother’s plasma passes to the child and vice versa due to the so-called blood-placental barrier.

Through strokes in the placenta, allowing the passage of red blood cells from the fetus to the maternal circulation. When the fetus has Rh + factor blood, the antigens in its red blood cells will stimulate the production of anti-Rh antibodies in the maternal immune system. These antibodies will settle in the maternal plasma, which may cause lysis in the fetal red blood cells.

Second risk pregnancy

If a second pregnancy occurs, if the fetus is Rh + again, the maternal organism itself will already contain antibodies to that antigen and the fetus may develop fetal erythroblastosis.

Is it possible to make a diagnosis?

Yes. The diagnosis can be made by the blood typing of the mother and father early, including during pregnancy. The Coombs test uses human anti-antibodies and can detect whether antibodies are being produced. After the child’s birth, Rh – mother is injected with serum containing anti Rh, causing the application after delivery to destroy fetal red blood cells that may have passed through the placenta at birth or earlier.

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