Blood is an indispensable fluid for human existence. It is estimated that the average human being has in his circulatory system about 4.5 liters of bloodwhich is pumped almost entirely by the heart in one minute. This vital fluid enables the transport of oxygen and nutrients to the tissues, allows thermoregulation mechanisms to occur in homeotherms, transports the body’s immune cells and many other tasks that are essential for life.
The blood volume in a person of average weight is 7% (or 70 milliliters/kilogram of weight). If a severe injury occurs that promotes hemorrhage, urgent transfusion is considered to be required when bleeding exceeds 30% of total volemia (III). If this intervention is not performed soon, death is almost assured: due to low blood content in the system, the heart becomes unable to pump and lethal hypovolemic shock occurs. This event causes 80% of intraoperative deaths.
In these cases, it is necessary to know which blood types are present in the general population and their compatibility (or lack thereof). Here are the 8 blood types and their characteristics, moving away from the superficiality of the AB0 classification.. Don’t miss it.
How are blood types classified?
First of all, it should be noted that blood types are heritable and follow a Mendelian inheritance pattern.. To understand the lines to come, it is essential to have a background in genetics, even if only in broad strokes. We begin by saying that human beings are diploid organisms (2n), that is, each of our cells contains a series of paired chromosomes within the nucleus. Of each pair, one chromosome comes from the father and one from the mother.
On the other hand, each inherited gene has a number of variations, also known as alleles. An allele is dominant (A) when it is expressed independently of the allele of the paired chromosome, while it is recessive (a) if it requires its copy to be the same as it to manifest itself (aa). For a particular trait, a person can be homozygous dominant (AA), homozygous recessive (aa) or heterozygous (Aa). In the latter case, only the dominant allele (A) is expressed and the recessive allele (a) remains masked.
With this little genetics express class, it will be easy to understand why many of the allelic distributions in later sections. Here are the 8 types of blood groups according to their classification criteria, we present the 8 types of existing blood groups according to their classificatory criterion.
1. AB0 system
This group is the best known of all and, undoubtedly, the most medically significant. The AB0 gene that determines this quality is triallelic, which means that it is present in 3 different alleles. The A and B alleles are dominant (codominant), while the 0 is recessive.so it is less likely to be expressed. All this information is encoded on chromosome 9 of the human karyotype.
These genes encode the presence of antigens A, B or none of them (0) on the red blood cell membrane. A person with blood group A has A antigens in his erythrocytes, but also circulating anti-B antibodies (IgG and IgM type). The opposite is true for the group B person. On the other hand, those of group AB have no antibodies to any antigen and those of group 0 have no antigens, but do have anti-A and anti-B antibodies.
The combination of all these alleles can give rise to the blood groups we know, following the typical Mendelian inheritance pattern. Thus, if a person is B0 (group B inherited from the mother and 0 from the father) he/she will be group B, since the B allele is dominant over the 0 allele. For a person to be group 0, both alleles must be 0 (00)..
2. Rh system
The Rh factor is a protein integrated in the red blood cells that determines, depending on its absence (Rh), whether the person is Rh positive or Rh negative. which determines, according to its absence (Rh-) or presence (Rh+), two new blood types. This classification has nothing to do with the AB0 group (it is inherited separately), so one person can be AB Rh+ and another AB Rh- without any problem.
This characteristic may sound anecdotal, but it rarely poses a real danger to the fetus during pregnancy. If for any reason (a microhemorrhage, for example) the blood of an Rh+ baby enters the bloodstream of an Rh- mother during gestation, the mother will perceive the infant’s red blood cells as pathogenic and begin to destroy them at the immune level. This results in a condition known medically as “hemolytic disease of the newborn”, characterized by marked anemia in the infant.
3. MNS System
Again, another system named after 3 variants: M, N and S. It is determined by two genes (unlike the AB0 system), glycophorin A and B, which code for this protein on chromosome 4.. Their antigenic dynamics are much more complex than those of the previous groups, so we will leave them for another occasion.
4. Lutheran antigenic system
On this occasion, 4 pairs of allelic antigens are taken into account, due to the substitution of a single amino acid in the Lutheran glycoprotein, encoded in the genome of chromosome 19.. Antibodies against these antigens are very rare and, therefore, this blood group has not acquired the importance of AB0 or RH over time.
5. KELL system
In this case, the antigens that determine the blood group are K, k, Kpa, Kpb, Jsa and Jsb. Each of these antigens are peptides found within the Kell protein, which is essential in the membrane of red blood cells and other tissues.
This blood determination system is important, as it is one of the main responsible for is one of the main responsible for incompatibilities during transfusions.only surpassed by AB0 and RH. If a given patient has circulating Anti-K antibodies to a blood sample with the above surface antigens, it will destroy them by a process called hemolysis. This immune response can be very severe.
6. DUFFY System
In this case, it is not so much the group encoding the DUFFY antigen that is important as its effects. Incredibly, people who do not have this antigen on the surface of their erythrocytes appear to be resistant to parasitic diseases as well as to parasitic diseases. appear to be resistant to parasitic diseases such as malaria (caused by the (caused by Plasmodium vivax), since the pathogen cannot use this antigen as a receptor and enter the red blood cells to infect them.
7. KIDD System
The KIDD antigen (also known as Jk antigen) is found on a protein of erythrocytes. a protein on erythrocytes that is responsible for transporting urea in the bloodstream to the kidneys. This form of classification is also important, as individuals with Jk(a) alleles can create antigens for the Jk(b) blood groups, resulting in the above-mentioned hemolysis, which is to be avoided at all costs in the blood transfusion process.
8. Other systems
We could continue this list for much longer, as to date, 33 blood systems have been 33 blood systems have been developed on the basis of more than 300 antigens, as indicated by the International Society of Blood Transfusion.as indicated by the International Society of Blood Transfusion. Almost all of the genes coding for these antigens are encoded on autosomal (non-sex) chromosomes, so they follow typical Mendelian inheritance patterns.
Summary
As you may have seen, there is a whole world when it comes to talking about blood types if we move away from the classical AB0 system.. However, this is the most important of all, as all subtypes in this category have antibodies to another blood group, except AB. Therefore, if care is not taken, a blood transfusion between incompatible groups can lead to disastrous clinical results.
Beyond AB0, the Rh and KELL systems are very important, the former being of particular importance in gestation and pregnancy. Fortunately, mothers with an Rh factor incompatible with that of their children can undergo an immunization “vaccination” process, which prevents the maternal immune system from rejecting the Rh antigen during pregnancy. Undoubtedly, the field of blood compatibility is impressive.