Blood group

The human blood consists of liquid called plasma that comprises white and red blood cells, and platelets. The antibodies and antigens present in the blood help to identify one’s blood group. The proteinaceous substance inside the plasma is called antibodies. Antibodies are a part of body's natural defense.

They alert the immune system by identifying foreign substances, such as microorganisms, and destroying them. The protein molecules found on the surface of red blood cells are called antigens.

Blood group

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Major divisions of blood

ABO system defines four main blood groups.

  • Group A: It contains A antigens in the red blood cells with anti-B antibodies in the plasma.
  • Group B: It contains B antigens with anti-A antibodies in the plasma.
  • Group O: It contains anti-A and anti-B antibodies in the plasma, but antigens are absent.
  • Group AB: It contains A and B antigens, but antibodies are absent.

Sub-types of blood group

These main blood groups are sub-divided into eight types and each can be either RhD negative or RhD positive.  One can have any one of these eight blood groups:

  • A+ (A RhD positive) and A− (A RhD negative)
  • B+ (B RhD positive) and B− (B RhD negative)
  • O+ (O RhD positive) and O− (O RhD negative)
  • AB+ (AB RhD positive) and AB− (AB RhD negative)

Blood group

“O” blood group

The most common blood group is “O,” which is found in 48% of the UK population. Hospitals request blood group O very frequently, as half of the donor population has this blood group. The blood group O’s red blood cells are compatible and versatile. They are more compatible with other blood groups of the ABO system, but patients of this group can receive red blood cell transfusions only from their own group.

An important blood group is O negative, which is commonly called “universal.” Red blood cells can be received by patients with blood groups A, B, and O, irrespective of whether they are Rh positive or Rh negative. The O negative red cells are unique and can be safely given to a patient whose blood type is unknown or immediately unavailable.

Therefore, this blood type is necessary in departments such as Emergencies & Accidents; the demand for O negative blood in all hospitals is around 13% but only 7% of the population has this blood.

“AB” blood group

The AB group is the rarest of ABO, because it is found in only 1 in 25 donors. AB red cells can be transfused to patients with AB blood and so this is the rarest of its form. AB is the least requested blood type by hospitals and so it is important to ensure a close balance between collections and hospital requests. Patients with severe blood loss can be treated with the freshly frozen plasma produced by AB blood group. Hence, donors of AB blood group are given high importance.

Sometimes, in a year, the demand for AB positive rises occasionally. The hospitals rely on the female donor's support to receive blood and blood products during the time of demand. Around 1% of the donor population is AB negative, which is the rarest blood type. Since it is rarest, it is hard and difficult to find new donors and collect sufficient amount of blood.

“A” blood group

The second most common blood group found in the donor population is group A. The largest blood group does not mean it is all plain sailing, but it is undoubtedly one of the most requested blood groups by hospitals. Balancing the collections and demand is rigorous. Negative donors have a very important role in making platelets. Platelets are one of the blood components that help prevent bruising and stop bleeding.

Around 60% of platelets are used to help cancer patients. Platelets of group A are constantly in high demand, as they can be given to patients of all ABO groups, making them extremely versatile. A higher priority is given to ensuring a regular and consistent supply of platelets, which can last only up to 7 days (compared to 35 days for red cells).

“B” blood group

Blood group B is found in only 10% of donors. The South Asian (20%) and Black communities (25%) seem to have more group B individuals than the White European communities (9%). To ensure that the patient need for this blood group is met consistently, the clinics encourage new donors from communities such as Black, Asian, and other minorities.

The Black communities are more susceptible to sickle cell anemia and the South Asian communities to thalassemia. During such critical conditions, patients may require multiple transfusions, and sometime throughout their lives. It is important that patients receive blood that is tested extensively to better match their own during regular transfusions.

Around 1 in 7 patients, B negative donors can help Rh positive and negative patients from groups B and AB−. The B negative donors are more in demand, as the hospitals depend heavily on them for the required blood.


Wondering what blood groups are? Why do we have many types of blood group? Well, blood groups are complex chemical systems in blood cells, which differentiate a particular type from the other. Blood grouping is essential for various reasons including safe blood transfusion. Let us understand about blood groups, their types and the uses of blood group typing.

Blood groups and their types are a classification based on the presence or absence of certain chemicals in red blood cells. Here, we look at different blood groups, their types and the uses of blood group typing.

Types of Blood Groups

There are 4 types of blood groups: A, B, AB and O. This classification is based on the presence or absence of inherited antigenic substances on the surface of red blood cells (RBC).

The main blood grouping systems are the following

ABO group typing – The ABO blood grouping system is based on the two antigens and antibodies present in the blood. The antibodies present together with the antigens are

  1. Antigen A with antibody B
  2. Antigen B with antibody A
  3. Antigen AB has no antibodies
  4. Antigen nil (group O) with antibody A and B.

Rh group typing – This is the next most common blood grouping system, which determines the types of blood groups. The most important is D antigen which is absent in Rh negative individuals and can be produced in these individuals by sensitization only. The presence or absence of Rhesus antigen is denoted by + or – sign along with the A, B, AB or O blood groups.

Bombay blood group was found first in Bombay (now known as Mumbai) and hence the name. This type of blood group is rare. These people can donate blood to the people with ABO blood groups but cannot receive from any blood group donor apart from Bombay blood group people. These people do not have antigen H in their blood but antibody H is present. It is also called as HH blood group. The cause for Bombay blood group is not clear but is surely one of the important types of blood groups.

Specific tests for detection of H antigen have to be conducted to classify as Bombay blood group. This blood group is often confused as O blood group because of lack of antigens.

Red blood cell compatibility is important considering the health and safety of the person receiving a particular type of blood group. The red blood cell compatibility is seen among the various types of blood groups and is checked before blood transfusion to the recipient to avoid adverse reactions in recipient.

Of all the types of blood groups, blood group O is universal donor, as these people can donate to any other blood groups. However, they can receive only from O blood group individuals as they do not have any antigens (A or B) on the surface of RBC.

The blood group AB is universal recipient as these people can receive from any blood group. However, they cannot donate to others apart from AB blood group as they have both antigens (A and B) on the surface of RBC.

Blood group typing in done in specified labs in a specific manner. Collect the sample of blood in test tubes. Mix the blood with three different reagents including either of the three different antibodies, A, B or Rh antibodies and look for agglutination. Look into the each test tube and check if the test tube containing A antibody, B antibody or Rh antibody is agglutinated and determine the blood group accordingly. The agglutinations happen if the antibody matches the antigen present in the blood. The antigen and antibody bind in the lock and key model and hence the formation of agglutinations.

The uses of blood group typing are as follows

Blood Transfusions: This is one of the main uses of blood group typing. The blood group typing plays a major role here, as certain blood groups are compatible and some are not. If mismatched transfusion occurs it can lead to anaphylactic reactions leading to death.

Hemolytic Disease Of The Newborn: This can occur in pregnant women carrying fetus with a different blood group and can lead to destruction of fetal hemoglobin due to antibodies produced by the mother. Knowing the right type of blood group in such cases is one of the important uses of blood group typing.

Paternity Testing: Only certain blood group combinations from parental blood groups are passed on to the offspring from the parents. Hence, the blood group typing can be used to help in paternity testing as well.

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For any living organism to survive in this world, they require proteins, nutrients and oxygen.

r transfer these substances to all parts of cells of the body their need to be some transport. Blood acts as transporter in the body. It accounts 7% of human body weight with an average density of 1060 kg/m3 for adult an average volume of blood is five liters. It is composed of plasma and different types of cells. Blood constitutes different type of corpuscles in it. They are known red blood corpuscles, leukocytes and thrombocytes. For those who want to know how many types of blood groups in human body:

Red blood cells constitute 45 % of blood; plasma is about 54.3% and leukocytes of 0.7%. Colour of blood is red, it is obtained by a substance which is present in it is called hemoglobin. A blood is decided based on the presence of antigens on the surface of red blood cells. Blood types are inherited and represented by contributions from both parents. So far International Society of Blood Transfusion had recognized 35 human blood group systems. Here are the main blood group and blood type

Why Do Blood Types Differ:

Blood is made of up of red and white blood cells, plasma and proteins. The plasma has antigens floating in it which is responsible for offering immunity to the body. Antigens are of two types, A and B, which produce different antibodies to fight the disease causing germs. People with O blood group have both the antibodies. This difference in antibodies create resistance to some diseases and vulnerable to others.

Percentage Of Blood Groups In India:

As per study, the most common blood group in India is O with a 37.12% of population. The second most common blood group is B with a 32,26%, followed by A at 22.8%. AB is the least found blood in the Indian subcontinent.

Rarest Blood Type In India:

The rarest blood group is Bombay Blood group, found only in 0.01% of Indian population. It is most likely found in Mumbai locals and hence the name. Among this, the negative blood group is even more rare in occurrence than positive. It is estimated that only 15 donors are identified across India with this blood group.


The ABO blood group

The four different blood groups in the ABO system are A, B, AB and O. A person’s blood group is determined by a pair of genes, one gene inherited from each parent.

Each blood group is identified by its own set of molecules (called antigens), which are located on the surface of red blood cells. When a person needs a blood transfusion, the donated blood must match the recipient’s blood or complications will occur.

The Rh type blood factor

A person’s blood type used to be called their ‘Rhesus type’ but now we say ‘Rh type’. Your Rh type is determined by a different pair of genes to the ones that determine your ABO blood type (again, one inherited from each parent). Blood is either Rh-positive or Rh-negative, depending on whether certain molecules are present. A person who is Rh-negative will experience a severe immune-system reaction if Rh-positive blood gets into their bloodstream. 

Blood groups in Australia

A person’s blood group is described by the appropriate letter (A, B, AB or O) and by whether their blood is Rh-positive or Rh-negative. 

According to the Australian Red Cross Blood Service, the percentage of blood group frequency in Australia is: 

  • O positive – 40 per cent
  • O negative – 9 per cent
  • A positive – 31 per cent
  • A negative – 7 per cent
  • B positive – 8 per cent
  • B negative – 2 per cent
  • AB positive – 2 per cent
  • AB negative – 1 per cent.

Blood transfusion

A blood transfusion is the transfer of blood or blood components from one person to another. Transfusions are of red blood cells or other components such as plasma or platelets.

O negative red blood cells can be given to anybody if necessary, but it is always preferable to match the exact blood group. Australia has one of the safest blood supplies in the world, and donating blood here is a very safe process. 

Read more about blood transfusions and donating blood.

Rh blood factor and pregnancy

Problems can occur during pregnancy if an Rh-negative woman carries an Rh-positive baby. If blood cells from the baby travel across the placenta, the woman’s immune system will see the Rh-positive cells as a threat. Specialised white blood cells will make antibodies designed to kill Rh-positive blood cells. 

If the woman later conceives another Rh-positive baby, her immune system will flood the fetus with antibodies. These antibodies then destroy the baby’s red blood cells. If left untreated, this can result in severe anaemia or even death of the baby. This is called haemolytic disease of the newborn (HDN).

Preventing haemolytic disease of the newborn (HDN)

HDN is now rare, since Rh-negative mothers are immunised throughout their pregnancy and within 72 hours of giving birth, using an immunoglobulin made from donated blood products. The immunoglobulin breaks down the baby’s red blood cells inside the mother’s bloodstream before her immune system has time to react.


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