How Many Genotypes and Phenotypes are There in the ABO Blood Group in Humans

Introduction

There are six different genotypes and four different phenotypes in the ABO blood group in humans. The genotypes are IAIB, IAIA, IBIB, IOIO, IAIO, and IBIO. The phenotypes are A, B, AB, and O. In this article, we will learn about the phenotypes and genotypes of the ABO blood group, how the antigens express themselves in the human body, and the history of the ABO blood group.

ABO Blood Group in Humans

The ABO Blood Group System is used to denote the presence of one, both, or neither of the A and B antigens on RBCs (erythrocytes). Antigens are any substance (chemicals, bacteria, viruses, etc.) from the environment that causes the immune system to produce antibodies against it. Immune systems produce antibodies, also known as immunoglobulins, when foreign substances, or antigens, are present. The ABO Blood Group System is used in human blood transfusions.

ABO Phenotypes

The four basic ABO phenotypes are A, B, AB, and O. The immune system forms antibodies against whichever ABO Blood group Antigens are not found on the individual's erythrocytes. For example, an individual in group A will have antibody B, and an individual in group B will have antibody A. Blood group AB does not have antibody A or antibody B. Also, this type of blood group is very rare. Blood group O has both antibodies A and B. People with blood group O are often called "universal donors."

The ABO antibodies are formed naturally in the body. The antibodies are produced when, in the immune system, there is a loss of antigen or missing antigens.

How blood types are related to six different genotypes

To know whether the A or B characteristics are present in a blood sample, a blood test is used. It is not possible to determine the exact genotype from a blood test result of either type A or type B. If someone has blood type A, they must have at least one copy of the allele A but they also could have two copies. The genotype of this type of blood group is either AO or AA. Likewise, people with blood group B could have a genotype of either BO or BB. People with the blood group AB have both A and B alleles, thus, their genotype must be AB. Similarly, blood group O has neither allele A nor B, the genotype being OO.

Expression of ABO Blood Group

The ABO blood group antigens are expressed in a wide variety of human tissues and are mostly present in the epithelial and endothelial cells.

The ABO blood groups are regarded as RBC antigens, where each human RBC expresses approximately 1 to 2 million ABO blood group antigens.

Blood cells like T cells, B cells, and platelets have ABO blood group antigens that have been absorbed from the plasma. ABO blood group antigens are also found in saliva and all body fluids, the cerebrospinal fluid is an exception.

History of ABO Blood Group

The ABO blood group was first discovered by Karl Landsteiner, an Austrian physician who was working at the Pathological-Anatomical Institute of the University of Vienna, which is now called the Medical University of Vienna. In 1900, he found that the erythrocytes or RBCs clumped together or agglutinated when mixed in test tubes with sera from different persons and that some human blood also agglutinated with animal blood. This was the first proof that blood variations exist in humans.

Karl Landsteiner was awarded the Nobel Prize in Physiology or Medicine in 1930. He referred to the specific blood group interaction as isoagglutination in his research paper. Also, he introduced the concept of agglutinins or antibodies, which is the actual basis of the antigen-antibody reaction in the ABO blood group system.

Conclusion

In this article, we learned about the phenotypes and genotypes of the ABO blood group, how the antigens express themselves, and the history of the ABO blood group. Nonetheless, the ABO blood group holds the utmost importance for human blood transfusion, and more focus should be given to this topic for further research studies.