What is the Rh factor?

The Rhesus FactorAny Rh Factor is a protein found on the surface of erythrocyte cells that carry oxygen in the blood.

This protein is not present in all people. People who have it are Rh positive (Rh+) and those who don’t have Rh negative (Rh-)-. Over 85% of the population is Rh+.

The name of the Rh factor comes from experiments carried out in 1937 by scientists Karl Landsteiner S Alexandre S. Weiner with rabbits and Rhesus monkeys (mulatto monkeys).

The Rh and ABO blood classification system

There are many blood classification systems, at least 30, but the best known and one of the most used is The ABO system and the Rh factor.

The ABO system classifies blood types into four general groups: A, B, O, and AB. Group A and group B are designated according to the presence of some blood or other antigens. Group O has neither and group AB has both.

Each of them can be classified as positive or negative depending on whether the Rh Factor.

Combining the ABO system and the Rh factor, there can be 8 blood groups: A-, B-, AB-, O-, A+, B+, AB+ and O+.

What exactly is the Rh factor?

The Rh factor blood classification system involves more than 50 antigens on the surface of red blood cells or erythrocytes.

Antigens are protein fragments capable of causing the immune system to react and synthesize antibodies specifically against them. What is known as humoral immunity.

The most prominent Rh factor antigen is the D Antigen, which usually causes strong immune responses in people who do not have it (Rh-).

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There are two alleles or genetic variants of this Rh antigen. OD, which is the dominant allele, eod, which is the recessive allele. Each person’s cell has one pair of each chromosome, so it has two alleles of the D antigen, one inherited from the mother and one inherited from the father, which can be the same or different.

Rh- people have both recessive d alleles (these people are dd). Rh+ people have at least one dominant D allele (these people can be dd or dd).

Importance of the Rh factor

When a person is Rh+ it indicates that their red blood cells express these antigens on their membrane. Being Rh- indicates that these antigens are not expressed.

Rh- people have other harmless variants of proteins on the surface of red blood cells. These variants have no antigenic capacity and are not attacked by the immune system.

Rh People when they come into contact with sRh+ blood will trigger an immune response recognizing Rh+ blood cells as an aggression. It’s a bit similar to what happens during an infection.

Humoral immunity will kick in and antibodies will be synthesized to attack Rh antigens. For this reason, it is very important to know the Rh factor to perform blood transfusions.

Rh incompatibility in pregnancy

the baby and its mother are two different people and may have a different Rh factor.

The fetus begins to form its own red blood cells around the sixth week of gestation. If the fetus is Rh+ the Rh antigens will be expressed on the surface of its red blood cells.

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If the mother is also Rh+ nothing happens, but if the mother mother is Rh- she will react against fetal red blood cells if their blood comes into contact.

The consequence is serious. The fetus may develop Erythroblastosis fetalis, also known as hemolytic disease of the newborn.

This only occurs if the mother is Rh- and the fetus is Rh+. This means that the father has to be Rh+, because if the mother and father are Rh- they cannot have Rh+ children.

If during pregnancy or childbirth the baby’s Rh+ blood comes into contact with the mother’s Rh- blood, the mother’s immune system will produce antibodies that attack the baby’s blood causing its red blood cells to be destroyed.

There are no risks to the life of the mother, except rare complications, but in the fetus it can lead to serious problems such as jaundice, anemia, heart damage or brain damage. In the worst case, the baby can die.

Prevention of Rh incompatibility

The development of antibodies against the Rh factor requires prior sensitization, that is, that the immune system has had previous contact with the antigens. That’s why in first-time mothers the risk is lower.

Knowing the mother’s Rh factor, it can be prevented by administering Rh Immunoglobulin (RhIg). This treatment is only effective for mothers who are not yet sensitized.

In already sensitized mothers, it is necessary to monitor the pregnancy and be prepared for what may happen, including the possibility of the newborn needing a blood transfusion.

This risk also exists in blood transfusions, but it is very rare for problems to occur, as the Rh factor is one of the basic determinations carried out in blood banks.

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