Blood Groups: Red blood cells, white blood cells, and platelets are all contained in a liquid called plasma. Antibodies and antigens in the blood help to identify your blood type. Antibodies are proteins that are present in the blood. They are a natural aspect of your body’s defences. They detect foreign things, such as pathogens, and notify your immune system, which then eliminates them. Protein molecules located on the surface of red blood cells are known as antigens.

Let us learn more about blood groups and their types by reading this article. This article covers blood groups, the ABO blood grouping system, the genetic basis of blood groups, different types of blood groups, the composition of blood and much more. Read on to find out more interesting facts about blood and blood groups.

Blood Groups Definition

The genetically determined system by which blood can be classified into different groups according to the presence or absence of agglutinogen, i.e., antigens on the surface of RBCs and the antibody in the blood plasma, is called the blood grouping system.

What is Blood and How Blood Groups Vary in Humans?

The blood is considered as a specialized liquid connective tissue and it is the main component of the circulatory system of many animals, including humans. The blood of human beings differs in certain aspects though it appears to be red in colour. One of the remarkable features differentiating the blood is the blood groups.

In humans, the blood groups are divided based on the presence or absence of two important components, i.e., the type of antigens present or absent on the surface of RBCs (erythrocytes) cells, and secondly, the type of antibodies present or absent in the blood plasma.

What is Blood Made of?

Blood can be broadly classified into two parts; the plasma and the formed elements. The composition of the blood is as shown in the flowchart below:

Blood Types and System

To donate or to accept blood, a person has to know his/her blood group! In the year \(1900,\) an Austrian Scientist called Karl Landsteiner discovered the ABO blood grouping system.

How Karl Landsteiner Discovered this ABO Blood Grouping System?

In \(1900,\) Karl Landsteiner observed that some of the blood samples of his experiments showed agglutination, i.e., formed clusters. This experiment made the path for his discovery of the “ABO blood group system”. For this, he was awarded the Nobel Prize.

ABO Blood Group System

ABO blood group system is based on the presence or absence of two surface antigens on the surface of red blood cells, namely antigen \(‘A’\) and antigen \(‘B’.\) Similarly, the plasma of different individuals contains two natural antibodies, i.e., the proteins that are produced in response to antigens. Based on the antigens and antibodies agglutination, four blood groups have been defined in humans, i.e., \(A, B, AB\) and \(O.\)

\(ABO\) Blood Group System through the table below:

Blood Group	Antigens on RBCs	Antibodies in Plasma
\(A\)	\(A\)	anti-\(B\)
\(B\)	\(B\)	anti-\(A\)
\(AB\)	\(A\) and \(B\)	Nil
\(O\)	Nil	anti-\(A\) and anti-\(B\)

Genetic Basis of ABO Blood Groups in Humans

Can you think of why our blood grouping system has been named ABO only and not anything else?? The answer to it is as follows:

1. The blood groups in humans are controlled by a single gene \(‘I’\) (\(I\) represent isohemagglutinin) which represents the production of glycoprotein or antigen present on the surface of the RBCs.
2. Blood groups are represented by a set of three allelic expressions namely, \(‘{I^A}’,\,'{I^B}’\) and \(‘i’.\) Any individual will carry two of these three alleles. As three alleles of a gene are involved in the ABO blood grouping system, it is a great example of multiple allelism, i.e., a character controlled by more than two alleles.
3. The allele \({I^A}\) produces a glycoprotein \(A\) or antigen \(A,\) in particular, it produces \(N\)-acetylgalactosaminyltransferase enzyme which recognizes \(H\) antigen present in the RBC membrane and adds \(N\)-acetylgalactosamine to the sugar part of \(H\) antigen to form \(A\) antigen.
4. The allele \({I^B}\) produces a glycoprotein \(B\) or antigen \(B,\) in particular, it produces Beta-galactosyltransferase enzyme which recognizes \(H\) antigen present in the RBC membrane and adds Beta-galactose to the sugar part of \(H\) antigen to form \(A\) antigen.
5. But the allele \(‘i’\) does not produce any enzyme and thus no specific antigen or glycoprotein.
6. The allele \({I^A}\) is dominant over \(‘i’\) and allele \(IB\) is also dominant over \(‘i’.\)
7. Allele \(‘i’\) is the recessive allele.
8. When the alleles \({I^A}\) and \({I^B}\) are together they are codominant and both the glycoprotein \(A\) and \(B\) are produced.
9. Hence, the blood group is determined by the presence or absence of one or both the blood glycoproteins, i.e., group \(A\) has glycoprotein \(‘A’,\) group \(B\) has glycoprotein \(‘B’,\) group \(AB\) has both the glycoproteins while group \(O\) has neither of them.

Table showing blood groups with their gene combinations and sugar moiety on the surface on RBCs. \(‘i’\)

Blood Group	Gene Combination	Sugar moiety added to form glycoprotein
\(A\)	\({I^A}\,{I^{A – }};\,{I^A}i\)	\(N\)-acetylgalactosamine
\(B\)	\({I^B}\,{I^{B – }};\,{I^B}i\)	Beta-galactose
\(AB\)	\({I^A}{I^B}\)	\(N\)-acetylgalactosamine, Beta-galactose
\(O\)	\(i\,i\)	No sugar

Rh Grouping

Have you ever heard of the blood being called positive blood groups or negative blood groups? Why do some of us have \( + ve\) and some have \( + ve\) blood group? Other than the ABO blood group system, another important system is the \(Rh\) blood grouping system.

What does \(Rh\) Stand for?

\(Rh\) stands for the term ‘Rhesus’, i.e., a monkey called Macaca mulatta in whose blood, this \(Rh\) factor or \(Rh\) antigen was first discovered by Landsteiner and Wiener in \(1940.\)

What is the \(Rh\) Factor?

A special antigen called \(Rh\) antigen similar to one present in Rhesus monkeys is observed on the surface of RBCs of the majority like nearly \(80\% \) of humans and this is known as \(Rh\) factor or \(Rh\) antigen. This factor decides whether the blood group is positive or negative.

1. A person with this \(Rh\) factor in their blood is considered \(\left( {Rh} \right) – \)positive \(\left( {Rh + ve} \right)\) and those in whom this antigen is absent are considered \(Rh\)-positive \(\left( {Rh + ve} \right).\)
2. An \(Rh – ve\) person, if exposed to \(Rh + ve\) blood, will form specific antibodies of IgG class against the \(Rh\) antigens.
3. Therefore, the \(Rh\) group should also be matched before blood transfusion.

Are There Any Other Blood Groups Apart from ABO?

Yes, based on other antigens apart from antigen \(A\) and antigen \(B,\) there are other blood grouping systems also present. Let us discuss a few of such systems.

Bombay Blood Group

The Bombay blood group is very rare and in India, one in \(7,600\) to \(10,000\) are born with this type of blood group. This blood group was first discovered in Bombay (present Mumbai) by De Y M Bhende in the year \(1952.\)

Bombay blood group is also called \(‘hh’\) because the individuals with the rare Bombay phenotype \(\left( {hh} \right)\) do not express \(H\) antigen (also known as substance \(H\)), the antigen which is present in blood group \(O.\) Bombay blood group does not have \(A\) or \(B\) antigens and hence this was first mistakenly typed as \(O\) blood. It was only when a specific test was conducted for \(H\) antigen which differentiates blood group \(O\) from the Bombay blood group.

Duffy Blood Group

The Duffy blood group is a type of blood group where its antigen which is termed as the “Duffy Antigen Receptor for Chemokines” (DARC) or the “Duffy chemokine receptor” serves not only as blood group antigen but also as a receptor for a family of proinflammatory cytokines termed chemokines and as a receptor for Plasmodium vivax malaria parasites.

How to Know Your Blood Group?

Let us now know how the test to determine our blood group is carried out. For this, we need a blood test conducting kit which includes a three-cavity glass slide, ethanol, sterile toothpick and needle, anti-serum \(A, B\) and \(D\) and lastly, the blood sample.

1. Firstly, swab your finger with ethanol then press the tip of your finger and prick with a sterile needle.
2. Add one drop of blood to all the three cavities of the sterile glass slide and to the first cavity add anti-serum \(A,\) add anti-serum \(B\) to the second cavity and anti-serum \(D\) for the last cavity.
3. Now using different sterile toothpicks mix the blood samples with the respective anti-serum and allow for a few minutes.
4. Now, we can identify the blood group by the agglutination factor.

An Experiment Showing B \( + ve\) Blood Group

Let us know how to identify the blood group through the given chart below:

Blood group	Antiserum A	Antiserum B	Antiserum D
A\( + ve\)	Agglutination	No Agglutination	Agglutination
A\( – ve\)	Agglutination	No Agglutination	No Agglutination
B\( + ve\)	No Agglutination	Agglutination	Agglutination
B\( – ve\)	No Agglutination	Agglutination	No Agglutination
AB\( + ve\)	Agglutination	Agglutination	Agglutination
AB\( – ve\)	Agglutination	Agglutination	No Agglutination
O\( + ve\)	No Agglutination	No Agglutination	Agglutination
O\( – ve\)	No Agglutination	No Agglutination	No Agglutination

By seeing the above table, the blood group test is conducted and identified.

Significance of Blood Groups

1. A blood group test helps the individual to know his/her blood group.
2. It helps in the proper transfusion of blood.
3. Knowing the blood group also helps the couples plan pregnancy and avoid the chances of erythroblastosis foetalis.

Which Blood Groups are “Universal Donor” and “Universal Recipient”?

If a patient is in need of blood, some individuals will go and donate blood. But can the patient’s body accept all the types of blood from different blood groups? No!
1. Blood transfusion plays a major role in saving or killing a person.
2. During the blood transfusion, the blood of a donor has to match with the blood of the recipient.

Blood Group	Donor’s Group	Recipient’s Group
\(A\)	\(A\) and \(O\)	\(A\) and \(AB\)
\(B\)	\(B\) and \(O\)	\(B\) and \(AB\)
\(AB\)	\(AB, A, B\) and \(O\)	\(AB\)
\(O\)	\(O\)	\(A, B, AB\) and \(O\)

Table showing donors and recipients of the four blood groups in human beings.
3. From the above table, it is evident that blood group \(‘O’\) can be donated to persons with any blood group and hence, the person with the blood group \(‘O’\) is called a universal donor.
4. A person with \(\left( {‘AB’} \right)\) blood group can accept blood from any person with \(AB\) as well as the other groups of blood and hence such a person is called a universal recipient.

Blood Group Related Disorders

Can the blood groups incompatibility cause any disease? How are diseases caused due to the factors related to blood groups? Can blood groups be associated with malaria? Let us learn more about all this below:

Erythroblastosis foetalis: A Disease Due to Rh Incompatibility During Pregnancy

A special case of \(Rh\) mismatching is seen when the father’s blood is \(Rh\)\( + ve\) and the mother’s blood is \(Rh\)\( – ve.\) In this case, if a \(Rh\)\( – ve\) mother is pregnant where the blood of the foetus is \(Rh\)\( + ve,\) then \(Rh\) antigens of the foetus do not get exposed to the \(Rh\) \( – ve\) blood of the mother in the first pregnancy as the two types of blood are clearly separated by the placenta.

However, during the delivery of the first child, there is a possibility of exposure of the maternal blood to small amounts of \(Rh\) antigens from the foetus having \(Rh\) \(+ ve\) blood. In such cases, the mother starts preparing antibodies against Rh antigen in her blood.

In case of her second or subsequent pregnancies, the \(Rh\) antibodies from the mother who is \(Rh\) \( – ve\) can leak into the blood of the foetus with \(Rh\) \( + ve\) blood and this destroys the foetal RBCs, which leads to haemolytic anaemia that could be fatal to the foetus. In worst cases, this leads to the death of the baby. This condition is known as “Erythroblastosis foetalis”.
Drawing showing Erythroblastosis foetails in a pregnant woman.

Can Erythroblastosis Foetalis be Avoided?

Yes, this condition can be avoided by administering anti-Rh antibodies to the mother immediately after the delivery of the first child.

Connection Between Duffy Blood Group and Malaria?

Malaria is a protozoan disease caused by the microorganism Plasmodium vivax through the bite of a female Anopheles mosquito. The Duffy blood group is a type of blood group where its antigen which is termed as the “Duffy Antigen Receptor for Chemokines” (DARC) or the “Duffy chemokine receptor” serves not only as blood group antigen but also as a receptor for a family of proinflammatory cytokines termed chemokines and as a receptor for Plasmodium vivax malaria parasites.

DARC might play a role as a scavenger on the red blood cell surface to eliminate the excess toxic chemokines produced in some pathologic situations.

Individuals with the Duffy-negative phenotype are resistant to this malarial parasite invasion and the molecular mechanism that gives rise to the phenotype \(Fy\left( {a – b – } \right)\) in black individuals can be associated with a point mutation \( – 33\, TC\) expressed in the homozygous condition in the FYB allele. Recently, this point mutation has been described in heterozygosity in the FYA allele in other malaria-endemic regions and until now we do not know if it confers a certain degree of protection against Plasmodium vivax infection.

Blood Clotting

Blood clotting which also refers to haemostasis is the formation of a gel-like or clot-like structure, preventing bleeding or loss of blood, i.e., haemorrhage in cases of injured blood vessels. It also occurs in a blood sample drawn from the body and kept in a plain test tube or a vial.

The straw-coloured liquid, called serum, refers to plasma minus blood coagulation factors. The gel or a clot consists of a network of insoluble protein fibres called fibrin in which the formed elements of blood get entrapped. Blood clotting, coagulation or the process of gel formation consists of a series of chemical reactions to result in the formation of a fibrin network.

Summary

Through this article, we learnt how important Blood groups are and what are the types of blood groups. By knowing our blood groups, it will be very easy to transfer or help needy people. People should be aware of their blood groups and their related diseases. Pregnant women can take medicines to avoid Erythroblastosis foetal.

Frequently Asked Questions (FAQs) on Blood Types

Q.1. Is O \( + \) is a universal donor?
Ans: No, the O \( – ve\) blood group is considered the universal donor. This is because the O \( – ve\) blood group does not have \(A\) or \(B\) antigens on the surface of the cells and also \(Rh\) factor is absent.

Q.2. Which is the rarest blood group in the world?
Ans: The \(O\) negative blood group is very rare and the main disadvantage of this blood group is, if an O \( – ve\) blood group person met with an accident and needs immediate blood, then the patient has to get an O \( – ve\) blood transfusion and getting this group of blood is difficult.

Q.3. Who is considered the father of the blood group?
Ans: An Austrian scientist called Karl Landsteiner discovered the ABO blood group system and is considered the father of the blood group.

Q.4. Which is the best blood group?
Ans: \(‘O’\) blood group is considered to be the best for health. Person’s with \(‘O’\) blood group have a lower risk of reactions and inflammation and also have reduced risk of heart diseases.

Q.5. How is Corona infection related to blood groups?
Ans: The research and the study says that symptomatic individuals with blood types \(B\) and \(AB\) who were \(Rh\)-positive were more likely to test positive for COVID- \(19,\) while those individuals with blood type \(‘O’\) were less likely to test positive. (This theory is still going through extensive research and is yet to be confirmed by experts).

Now that you have a comprehensive article on Blood Groups, we hope you prepare well for the exam. If you face any issue while preparing, do let us know about it in the comments section below and we will get back to you soon.