ABO SYSTEM: INCOMPATIBILITY, INHERITANCE AND PROOF - BIOLOGY - 2024

The ABO system is the most important typification that classifies red blood cells according to the antigen or agglutinogen they have on their plasma membrane. The ABO system emerged in the year 1900 thanks to the discovery of Karl Landsteiner, and it was also the first system for typing red blood cells known up to that time.

Landsteiner observed that the erythrocytes of one person and another were differentiated by the presence or absence of certain antigens on their membrane. The first to be discovered were agglutinogens A and B.

Reagents to determine blood group. Source: Photo taken by the author MSc. Marielsa Gil.

He saw that some individuals had agglutinogen A, or B and others had neither A nor B and named it O. Later, agglutinogen AB was discovered. Then other red blood cell typing systems emerged such as the Lewis system and the Rh system. Of these, the Rh system has been the second most important, after ABO.

The Rh system was discovered in 1940 by Alexander Salomon Wiener and has long been considered an inseparable complement to the ABO system in typing blood groups. Subsequently, other less important typing systems were described, such as the MNSs, Duffy, Kell and xg systems, which are the best known.

However, there are many others such as the Chido / Rodger, Cartwright, Knops, Kidd, Cromer, Colton, JMH, Lutheran, P, Diego, Ok, Raph, Wienner, Gerbich, Indian system, among others, that have not had the utility and the clinical importance of the ABO and Rh system.

Due to the importance of Karl Landsteiner's discovery, he was recognized for his great work and for this he received the 1930 Nobel Prize in Medicine and Physiology.

Importance of the ABO system

Before the knowledge of the ABO system, blood transfusions were a great challenge, because due to ignorance they were carried out randomly and more times they obtained fatal results than those that were correct.

Today it is known that blood transfusions must be governed according to the type of blood group that the individual presents. Furthermore, the ABO system is of crucial importance in areas such as obstetrics and neonatology to prevent blood incompatibilities and treat existing ones between the mother and the fetus respectively.

On the other hand, the determination of the blood group has served to clarify legal discrepancies regarding paternity disputes, since the blood group of an individual is inherited by the parents in compliance with Mendelian laws. Therefore, the percentage probability of the possible blood group in a baby can be determined.

For example, if the mother has an AO genotype and the alleged father is genotypically AA but the child expresses a B phenotype, according to Mendelian laws it is impossible for that individual to be the father, because within the possible combinations group B is not a option. See the following table:

Table 1: Explanation of the previous example. Source: Prepared by Marielsa Gil

Likewise, the determination of the blood group has served in forensic pathology to determine if the blood found at the crime scene belongs to the victim or the aggressor and thus to be able to reach the person responsible for the act.

Finally, it should be noted that knowing a person's blood group can save life in case of accidents. That is why, in some countries, it is mandatory for everyone to carry a card with them specifying their blood group. It can be in the identity document, in the medical certificate or in the driver's license.

ABO system blood incompatibility

There are many medical procedures, especially surgical, that involve great loss of blood (hypovolemic shock), in which it is necessary to perform blood transfusions to the patient. For this, it is essential that the recipient's blood group be known and thus find the perfect donor for that person.

If the patient receives the wrong blood, his organism will react against the red blood cells received by the agglutinins present. On the other hand, there may also be ABO group incompatibility in mothers with blood group O if the child is A, B or AB.

Because the mother is O, she will contain anti A and anti B agglutinins in her plasma. These agglutinins can cross the placenta, causing lysis of the baby's red blood cells. The child may be born with jaundice and require phototherapy.

However, the consequences of ABO system incompatibilities are not as severe as those of the RhD system in the baby.

Presence of agglutinins in plasma

Incompatibility reactions occur because the recipient's plasma contains natural agglutinins against the antigen present on the donor's erythrocyte.

For example, a patient in group A will have agglutinins against antigen B, while a patient in group B has natural agglutinins against antigen A.

Likewise, a patient O presents agglutinins against antigen A and antigen B and a patient in group AB does not contain agglutinins.

These agglutinins attack the received erythrocytes, causing their hemolysis. This will lead to severe hemolytic anemia called a post-transfusion hemolytic reaction or a hemolytic transfusion reaction.

Blood transfusions

In this sense, doctors must take into consideration the compatibility chart. This table explains how blood transfusions can be carried out depending on the type of blood possessed by the recipient and the donor (see compatibility table).

It should be noted that the recipient-donor relationship is not reversible, since it is not the same to be the donor as the recipient. As a donor it can be given to certain blood groups, but as a recipient these can vary.

On the other hand, blood transfusions cannot always be done with whole blood, but there are other options: only red blood cells (red blood cells) or only plasma can be transfused.

For example: a person who has blood group A Rh + can donate whole blood to another A Rh + patient or only his red blood cells to a patient who is AB Rh +.

Now, if that same patient A Rh + was to be the recipient, he could receive whole blood from people whose blood group is A Rh + or A Rh -, while he could receive blood cells of O Rh + or O Rh - and only plasma of A + and AB +. See the compatibility table.

Table 2: Blood compatibility. ABO-Rh blood group compatibility chart. Source: Table taken from "Blood group." Wikipedia, The Free Encyclopedia. 7 Jun 2019, 02:18 UTC. 7 Jun 2019, 16:47Disadvantages of blood transfusions

Sometimes blood transfusions cannot be performed due to religious factors that prohibit such practice.

On the other hand, not everyone can be a blood donor, since there are specific conditions that can disqualify the individual for this action.

Among them, we find anemic patients, the elderly (> 65 years), people under 18 years of age, patients with past or present viral infections such as hepatitis B, HIV, parasitic diseases such as malaria, toxoplasmosis, bacterial infections such as leprosy, brucellosis, among other affectations.

As well as, people undergoing drug treatment eg: antibiotics, transfused or transplanted patients, promiscuous patients, among others.

Universal donor

An important analysis that can be highlighted in the compatibility chart is that blood group O Rh (-) can donate red blood cells to all blood groups. That is why it is called a universal donor, but you can donate whole blood or plasma only to another O Rh- equal to him.

And in the case that the O Rh- is the recipient, it can receive whole blood and blood cells only from another O Rh (-) patient, but instead can receive plasma of all types.

Universal receiver

In the same compatibility chart, it can be observed that in patients whose blood group is AB Rh +, the opposite occurs completely than with group O Rh -, since in this case AB Rh + is the universal receptor.

That is, you can receive red blood cells from anyone regardless of blood group, AB Rh + and AB Rh- whole blood, and AB Rh + only plasma. While you can donate plasma to all blood groups, as yours does not contain agglutinins; and whole blood or red blood cells only to another AB Rh +.

Hereditary nature of the ABO system

Epstein and Ottenberg in 1908 said that a person's blood group could be the result of inheritance from their parents.

In this sense, E. von Dungern and L. Hirszfeld two years later not only accepted that it was hereditary, but also that it complied with Mendel's laws, where groups A and B behaved as dominant factors and group O as recessive.

Every individual possesses genetic information that is phenotypically expressed. Genetic information is represented by two alleles, one provided by the mother and the other by the father.

Alleles can be two dominant. Example: AA, BB, AB, BA. They can also be two recessive (OO) or one dominant with one recessive (AO) (BO).

In the case of the two dominant and the two recessive, the information they possess will be expressed as is and they are said to be homozygous, but in the case of the combined alleles, that is, one dominant and one recessive, they are said to be heterozygous and they will phenotypically express the dominant allele.

Table 3: Blood group inheritance. Source: Barbecho C, Pinargote E. ABO System and A1 Subgroups In Patients From the Blood Bank of the Vicente Corral Moscoso Cuenca Hospital, 2016. Degree Thesis to qualify for the Bachelor of Clinical Laboratory degree Available at: dspace.ucuenca.edu.ec

Determination of blood group in the laboratory

Determining the blood group (ABO and Rh) is an easily performed test in any clinical laboratory.

For this, the laboratory must have a kit of 4 reagents. These reagents are nothing more than monoclonal antibodies that react with the corresponding antigen, these are: Anti –A, Anti B, Anti AB and Anti D or anti-Rh factor.

By confronting each of these reagents with a blood sample, the person's blood group can be determined. This is possible by analyzing the various reactions.

A positive reaction will be evident when gross (naked eye) agglutination of red cells is observed. Agglutination indicates that the antibody (reagent) found its corresponding antigen on the surface of erythrocytes, causing them to clump together.

Table 4: Expected reactions against the different monoclonal antibodies in each blood group. Source: Table prepared by MSc. Marielsa Gil. Information taken from: Laboratorios Wiener. Anti-A, Anti B, Anti AB monoclonal. Reagents for ABO blood group determination. 2000, Argentina.

Distribution of blood groups (ABO-Rh) in the population

Different blood groups are found in different proportions within the population. Some are very common and therefore it is easier to find a donor for them. This occurs for example in patients with group O Rh + (37%) or A Rh + (34%).

Others are of moderate frequency, for example: B Rh + (10%), A Rh- (6%) and O Rh- (6%) but on the other hand there are other extremely rare groups such as AB Rh + (4%), B Rh- (2%), AB Rh- (1%).

References

1. Cossio E, Solis A Castellon N, Davalos M, Jarro R. Typing of the ABO blood group and the Rh factor in the population of Totora-Cochabamba management 2012. Rev Cient Cienc Méd. 2013; 16 (1): 25-27. Available at: scielo.org.
2. Pérez-Ruiz L, Ramos-Cedeño A, Bobillo-López H, Fernández-Águila J. Blood groups ABO, RhD and multiple sclerosis. Rev Cubana Hematol Immunol Hemoter. 2011; 27 (2): 244-251. Available at: scielo.org
3. Agglutinin. Wikipedia, The Free Encyclopedia. 21 Aug 2017, 18:02 UTC. 7 Jun 2019, 03:14 en.wikipedia.org
4. Guzmán Toro, Fernando. The ethical and legal dilemmas related to blood transfusions in extreme situations. Phronesis, 2010; 17 (2), 185-200. Available at: scielo.org.ve
5. Pliego C, Flores G. Evolution of blood transfusion. Rev. Fac. Med. (Mex.) 2012; 55 (1): 35-42. Available at: scielo.org
6. Wiener Laboratories. Anti-A, Anti B, Anti AB monoclonal. Reagents for ABO blood group determination. 2000, Argentina. Available at: Wiener-lab.
7. Barbecho C, Pinargote E. ABO System and A1 Subgroups In Patients From the Blood Bank of the Vicente Corral Moscoso Cuenca Hospital, 2016. Degree thesis to qualify for the title of Bachelor of Clinical Laboratory Available at: dspace.ucuenca.edu.ec