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Introduction:
The human body has about 5 litres of blood which is more than a gallon. It keeps circulating continuously, carries oxygen and nutrients to different body parts, and helps remove waste. The blood comprises plasma, red blood cells, white blood cells, and platelets. Even though the basic component of blood remains the same, certain elements differentiate it between individuals. Blood is divided into the ABO and Rh blood group systems for differentiating. The red blood cells of each blood group contain a specific type of antigen on its surface that is not found in other blood groups.
The ABO Blood Group System
Blood is classified in blood groups ABO, Rh, and MN systems, along with several others. There are several other blood grouping systems, but one of the major systems is the ABO system. In this system, the blood is classified as A, B, AB, and O. This classification is done depending on the presence of specific antigens on the surface of red blood cells (RBCs) found in the blood. The surface of RBCs has antigen A in individuals with A blood group. Similarly, people with blood group B have the presence of antigen B. Individuals with the blood group AB have antigen A and antigen B present on the RBC surface. However, those with neither A nor B antigens fall into the blood group O.
Apart from antigens, the blood also contains antibodies in the plasma. These antibodies come into action if an incompatible blood type comes in contact. The plasma of blood group A contains anti-B antibodies. Blood group B contains anti-A antibodies. The plasma of the AB blood group does not have anti-A or anti-B antibodies. However, both anti-A and anti-B antibodies are present in the plasma of blood group O.
An individual’s blood group depends upon the genes inherited from parents. The most commonly found blood group is O.
The Rh Blood Group System
The Rh system indicates the presence of the Rh factor in the blood. The Rh factor of blood is determined by the presence or absence of RhD antigen. RhD antigen is a protein also found on the surface of red blood cells. People who have RhD antigen in their blood are called Rh-positive. In contrast, those without the RhD antigen are called Rh-negative. A + or – sign is used to indicate whether a person is Rh-positive or Rh-negative.
The ABO blood group system and Rh factor from the Rh system help determine the actual blood group of an individual. Therefore, there are a total of eight blood groups in humans.
- A+ or A positive
- A – or A negative
- B+ or B positive
- B – or B negative
- AB+ or AB positive
- AB – or AB negative
- O+ or O positive
- O – or O negative
Difference Between ABO and Rh Blood Group System
The ABO and Rh blood group systems can be differentiated based on certain parameters. Let us have a look at the difference between ABO and Rh blood grouping systems.
Antigens Present/Absent
ABO System: It classifies blood on the basis of the presence or absence of antigen A and antigen B.
Rh System: It classifies blood on the basis of the presence or absence of RhD antigen.
Phenotypes
ABO System: There are four phenotypes of the ABO blood group – A, B, AB, and O.
Rh System: There are two phenotypes – Rh-positive and Rh-negative.
Antibodies Present
ABO System: The antibodies present in the plasma are anti-A and anti-B antibodies.
Rh System: The antibodies present in the plasma are anti-D antibodies.
Non-Mendelian/ Mendelian Inheritance
ABO System: The inheritance of these blood groups follows the non-Mendelian inheritance patterns.
Rh System: This blood group follows Mendelian inheritance patterns.
Gene and Chromosome
ABO System: The gene is coded by the ABO gene. It is located on chromosome 9.
Rh System: The gene is coded by two linked genes – RhD and RhCE. These genes are located on chromosome 1.
Conclusion:
The ABO and Rh blood group system is of prime importance as it helps in differentiating blood. The blood of individuals who require blood transfusions is matched with the donor’s blood before carrying out a blood transfusion. Matching a blood group is essential because if the blood is not compatible, the recipient may suffer severe consequences, even death. When a recipient receives incompatible blood, the antibodies attack the red blood cells resulting in agglutination in the blood vessels, bursting of cells, and hemolysis, which can sometimes be fatal.
Pregnant women are also required to undergo a blood group test to ascertain the Rh factor of the mother and the baby. If the mother is RhD negative and the baby is RhD positive, it could lead to complications in pregnancy. With the advent of blood grouping systems, it has been possible to prevent unnecessary complications in blood recipients and pregnant women.
