Difference Between ABO Blood Group and RH Blood Group

Main Difference – ABO Blood Group vs RH Blood Group

ABO blood group system and RH blood group system are the most common types of blood group systems used for the blood typing. Each blood group system is used to determine the variation of different traits of the red blood cells. The surface antigens on the red blood cells determine the type of the blood. These antigens can be proteins, carbohydrates, glycoproteins or glycolipids. The main difference between ABO blood group and RH blood group is that ABO blood group is determined by the presence or absence of A and B antigens on the surface of the red blood cell whereas RH blood group is determined by the presence or absence of D antigen on the surface of the red blood cell. The two alleles that are encoded for the A and B antigens are I^A and I^B. The recessive allele is i. The two alleles that are encoded the RH blood group are D and d. The antigen is also called the ‘Rhesus factor.’

Key Areas Covered

1. What is ABO Blood Group
      – Definition, Determination, Types
2. What is Rh Blood Group
      – Definition, Determination, Types
3. What are the Similarities Between ABO Blood Group and RH Blood Group
      – Outline of Common Features
4. What is the Difference Between ABO Blood Group and RH Blood Group
– Comparison of Key Differences

Key Terms: ABO Blood Group, Antigen A, Antigen B, Antigen D, RH Blood Group, Rhesus Factor, Red Blood Cells

What is ABO Blood Group

ABO blood group is the major blood group system in human blood typing. It is determined by the presence or absence of the two antigens, antigen A and antigen B on the surface of the red blood cells. Three alleles can be identified when determining the ABO blood group. They are I^A, I^B, and i. The enzymes that attach acetyl galactosamine to the surface of the red blood cells are encoded by the I^A allele. The enzymes that attach Galactose to the surface of the red blood cells are encoded by the I^B allele. i allele encodes an inactive enzyme. Another gene called gene H encodes for the enzymes that attach fructose to the surface of the red blood cells. The addition of fructose is essential for the subsequent addition of monosaccharides to the red blood cells surface by the I^A and I^B alleles. The non-functional gene H may cause the formation of masked phenotypes in A, B, and AB blood types, which resemble the O blood type.  Four ABO blood group phenotypes can be identified based on the above three alleles. They are type A blood, Type B blood, type AB blood, and type O blood. The inheritance of the AB blood type follows non-Mendelian inheritance patterns. The associated anti-A and anti-B antibodies are produced in the serum by the sensitization to the environment during the first year of life. Therefore, anti-A and anti-B antibodies are IgM antibodies. The four phenotypes of the ABO blood group and their corresponding allele combinations are shown in table 1.

Table 1: Blood Types and their Allele Combinations

Figure 1: Blood types of the ABO blood group, their antigens, and antibodies

What is RH Blood Group

The RH blood group system is the second major blood group system in human blood typing. It is determined by the presence or absence of the D antigen on the surface of the red blood cells. Moreover, the RH blood group consists of 49 different antigens. However, antigen D is the most significant type of antigen among those 49 antigens. The D antigen is also referred to as the ‘Rhesus factor.’ The two alleles involved in the determination of the RH blood group are allele D and allele d. The allele D is dominant over allele d. The two phenotypes produced by the above two alleles are Rh-positive and Rh-negative. The two genotypes, DD and Dd, produce Rh-positive individuals whereas the genotype dd produce Rh-negative individuals. The anti-D antibodies are present in the serum of the Rh-negative individuals. Both ABO blood group and RH blood group are collectively used in the determination of the compatibility of blood types during a blood transfusion. The frequencies of the ABO and RH blood group systems in the United States are shown in table 2.

Table 2: Frequencies of the ABO and RH Blood Group Systems in the United States

Figure 2: Compatibility table of blood types for blood transfusion

Similarities Between ABO Blood Group and RH Blood Group

• ABO blood group and RH blood group are two types of systems used for the blood typing.
• Both ABO blood group and RH blood group are determined by the presence of surface antigens on the red blood cells.
• Both ABO and Rh blood group systems follow the Mendelian inheritance patterns.
• A combination of both ABO and RH blood groups are used in the determination of the blood type of an individual.
• Both ABO and Rh blood groups are cross-matched when a blood transfusion is needed.
• Anyone can receive O negative blood type in an absolute emergency.

Difference Between ABO Blood Group and RH Blood Group

Definition

ABO Blood Group: The ABO blood group is the major blood group system in human blood typing, which is determined by the presence or absence of two antigens, A and B on the surface of the red blood cells.  

RH Blood Group: RH blood group is the second major blood group system in human blood typing, which is determined by the presence or absence of the D antigen on the surface of the red blood cells.

Determined by

ABO Blood Group: The ABO blood group is determined by three alleles; I^A, I^B, and i.

RH Blood Group: The RH blood group is determined by two alleles, D and d.

Mendelian/Non-Mendelian Inheritance

ABO Blood Group: The inheritance of the AB blood type is an example of codominance. Therefore, the inheritance of the AB blood type follows the patterns of non-Mendelian inheritance.

RH Blood Group: The RH blood group follows Mendelian inheritance patterns.

Phenotypes

ABO Blood Group: The phenotypes of the ABO blood group are A, B, AB, and O blood types.

RH Blood Group: The phenotype of the RH blood group are Rh-positivity and Rh-negativity.

Antigens

ABO Blood Group: The ABO blood group comprises antigen A and antigen B on the surface of the red blood cells.

RH Blood Group: The Rh blood group comprises 49 different antigens along with the antigen D on the surface of the red blood cells.

Antibodies

ABO Blood Group: The ABO blood group comprises anti-A, anti-B antibodies in the serum.

RH Blood Group: The RH blood group comprises anti-D antibodies in the serum.

Conclusion

ABO blood group and RH blood group are the two major blood groups used in the blood typing of humans. Both blood types are determined by the presence or absence of different antigen types on the surface of the red blood cells. The ABO blood type is determined by the presence or absence of antigen A and antigen B on the surface of the red blood cells. The RH blood group is determined by the presence or absence of antigen D on the surface of the red blood cells. In the absence of a particular antigen on the red blood cell surface, the corresponding antibody develops in the serum. The main difference between ABO blood group and RH blood group is the types of antigens that determine the type of the blood in each blood group system.

Reference:

1.Dean, Laura. “The ABO blood group.” Blood Groups and Red Cell Antigens [Internet].U.S. National Library of Medicine, 01 Jan. 1970. Web. Available here. 14 Aug. 2017. 
2.Dean, Laura. “The Rh blood group.” Blood Groups and Red Cell Antigens [Internet].U.S. National Library of Medicine, 01 Jan. 1970. Web. Available here. 14 Aug. 2017. 
3.”ABO and Rh Blood Type Frequencies in the United States.” Human Blood: Table of ABO and Rh Blood Type Frequencies in the United States. N.p., n.d. Web. Available here. 14 Aug. 2017. 

Image Courtesy:

1. “ABO blood type” By InvictaHOG – Own work (Public Domain) via Commons Wikimedia
2. “Blood type compatibility chart” by twintiger007 (CC BY 2.0) via Flickr