Do you know your blood type? Do you know what differentiates one blood type from another? In the human species there are four blood groups of the ABO system (A, B, AB and O), related to the presence of certain antigens in the membrane of red blood cells.
Red blood cells are the most numerous figurative elements present in the blood. Each living being has a group of proteins different from any other being.
Thus, when, for example, a bacterium or a foreign organism penetrates the body, its proteins are not recognized (antigens) and the production of proteins called antibodies begins, which neutralize the antigens. Antibodies are specific: for each type of antigen, only one type of antibody is produced, with a complementary form to that of the antigen.
Index
- ABO and Rh System
- ABO system table
- How it works
- Blood transfusions
- Fetal erythroblastosis
- Solved exercises
ABO and Rh System
There are four types of blood and two factors (Photo: Pixabay)
ABO blood group system
The system includes the ABO blood types A, B, AB and O . People in group A have an antigen called agglutinogen A; those in group B, the agglutinogen B antigen; people in the AB group have both antigens; and those in group O have neither A nor B.
The group O (capital letter “O”) was initially called “group zero” (group 0), because it does not have antigen A or B, but it is currently more common to use the letter “O” for this group, although in some parts in Europe you still use the number zero (0).
Rh system of blood groups
Another system of classifying blood groups is called the Rh system (initials of Rhesus , the monkey genus in which this antigen was first discovered).
About 85% of human beings have Rh cells in their red blood cells and are called Rh positive ( Rh + ). Those without this antigen are Rh negative ( Rh- ).
Although several alleles are not involved in the inheritance of the Rh factor, for the purpose of blood group incompatibility, we can consider only a pair of alleles: R (dominant, makes this antigen appear) and r (recessive).
- Phenotypes: Rh + / Rh-
- Genotypes: RR or Rr / rr
Unlike antigens in the ABO system, the Rh antigen is not found in bacteria and, at first, a negative individual does not have antibodies in the plasma.
In general, Rh- individuals produce corresponding antibodies when they receive red blood cells with the Rh antigen, which can occur during pregnancy, childbirth or transfusions.
ABO system table
(Image: Reproduction | Wikimedia Commons)
How it works
Antigens are polysaccharides attached to the red cell membrane and their presence is controlled by three alleles located in the chromosome 9 pair. These alleles promote the synthesis of enzymes that add specific sugars to a precursor substance in the red cell membrane.
The A or I A allele conditions the formation of agglutinogen A; the B or I B allele conditions the formation of agglutinogen B; the O or i allele does not form these substances (the letter I comes from isoagglutination, which is the agglutination that occurred in the blood transfusion of individuals of the same species).
The alleles I A and I B are dominant over i . That is why people of genotypes I A I A and I A i have agglutinogen A, and people of genotypes I B I B and I B i , agglutinogen B.
Individuals ii have neither agglutinogen. Between alleles I A and I B there is codominance, so each provides its effect and the two substances appear.
In addition to agglutinogens in red blood cells, antibodies against these agglutinogens, called agglutinins or isoglutinins, can be found in plasma.
The term agglutinin is used to indicate that these antibodies cause red blood cells to agglutinate . Thus, antibodies prevent red blood cells from spreading in the body, helping in the process of phagocytosis by white blood cells.
Blood transfusions
Transfusions can be part of the treatment of some diseases (Photo: Reproduction | Freepik)
One of the main reasons why blood is tested for blood type is the need for transfusion.
Blood transfusion is done when a patient loses a lot of blood and his body is not able to replace what was lost alone. Transfusions can also be part of the treatment of some diseases.
The blood that will be donated for transfusions is separated into several elements: red blood cell concentrate, plasma (in turn, separated into several components), platelet concentrate, etc.
Each can be used according to the specific situation: in certain cases of anemia or acute hemorrhage , for example, there is a need for transfusion of packed red blood cells.
Plasma can be used when there is a deficiency of multiple coagulation factors and when commercial concentrates of these factors are not available (obtained by genetic engineering techniques).
Before transfusion, it should be noted whether the donor’s blood is compatible with the recipient’s blood. The recipient’s serum is mixed with the donor’s red blood cells to investigate the presence of antibodies against the antigens present on the latter’s red blood cells.
The person with blood type O does not have agglutinogens A or B in red blood cells, so we say that this group is a universal donor , since their blood, in the form of red blood cell concentrate, can be donated to people with A blood. , B, AB or O.
In practice, people preferably receive blood of the same type as yours. Type O blood cells should be used in patients of another blood group only in emergency situations.
Similarly, people in the AB group, because they do not have anti-A or anti-B agglutinins in the plasma, accept red blood cell transfusions from people with A, B, AB or O blood, being called universal recipients .
See the blood group compatibility scheme for red blood cell transfusion below:
Fetal erythroblastosis
Fetal erythroblastosis or hemolytic disease of the newborn (DHRN) can occur in children of Rh- mothers. If the son is Rh-, he will have the same pattern as the mother and there will be no incompatibility between them. If it is Rh +, a few days before birth and mainly during delivery, some of the fetus’ blood escapes into the maternal body, which is stimulated to produce anti-Rh antibody.
As this production is not immediate, the first child will be born without problems. However, in a possible second pregnancy, maternal antibodies , already concentrated in the blood, cross the placenta and can cause the red blood cells of the fetus to agglutinate.
To prevent fetal erythroblastosis, up to three days after delivery of the first Rh + child, the Rh- mother should receive an application of anti-Rh antibodies.
Summary of Content
In this text you learned that:
- The ABO system consists of 4 blood groups.
- Blood groups are: A, B, AB and O.
- Another classification system is the Rh system.
- Knowing the blood type is important for cases of transfusion.
