What is the blood grouping system

The blood group system is a combination of antigens that are categorized according to their homozygous (or phenotypic) antigenic relationships on the red blood cell membrane.

Erythrocyte antigenic determinants can elicit either a homozygous or heterozygous immune response. In the identification of human blood groups, the agglutination reaction is usually performed with specific human antisera. Each blood group system is inherited independently, and most of the genes controlling a blood group system are on the same chromosome.

To date, several blood group systems have been identified in humans, but the ABO blood group system is the most commonly used and important in clinical practice.

About the ABO Blood Group System

The first human blood group system was discovered by Karl Landsteiner (1900). The ABO blood group is inherited by three alleles: A, B and O. The A and B genes are dominant and the O gene is recessive. The A and B genes are dominant, and the O gene is recessive. Although there are no A and B antigens on O-type red blood cells, there are H antigens. H antigens are also the basis of A and B antigens. ABH antigens are not only found on red blood cells, but also can be present in body fluids 80% of the people have ABH antigens in their saliva, which is known as the secretory type; people who do not have ABH antigens in their saliva are known as the non-secretory type secretors. The ability to secrete is also under genetic control.

The ABO blood group system differs from other blood group systems in that it has “natural” antibodies, e.g., type A has anti-B antibodies, type B has anti-A antibodies, and type O has anti-A and anti-B antibodies. These antibodies are produced as a result of implicit immunization after birth with antigenic substances in the natural environment that have the same specificity.