ABO Blood Group System

Definition of blood groups

In 1901, the first blood group system was discovered by Austrian biochemist Karl Landsteiner. Landsteiner discovered that depending on the characteristics of a person erythrocytes and the presence of certain antibodies in their plasma to erythrocyte antigens, individuals could be categorised into various groups. These findings laid the fundamentals for safe routine transfusion of blood. He then started to separate the erythrocytes from the plasma taken from individuals blood and then mixed the plasma and erythrocytes created all the possible combinations and indicated that only number of combinations of erythrocytes and plasma resulted in the clumping of the erythrocytes. These arrangements of clumping showed us the

The ABO system consists of four blood groups; A, B, AB and O. Individuals can be divided into these by the ABO blood group system; this is according to the different type of antigen that is present on the surfaces of their erythrocytes. (Ahmed, 2007)

The antigens that determine ABO blood groups are oligosaccharide constituents of cell surface glycolipids and glycoprotein (Ahmed, 2007). The H antigen, which is located on chromosome 19, can be attached to type I or type II precursor chains. The H gene encodes an enzyme, L- fucosyl tranferase that adds L-fucose to the terminal galactose to form the H antigen (Ahmed, 2007). Individuals with with blood grioup A and AB contain the A gene which is found on chromosme 9. This gene encodes N-acetylgalactosaminyl transferase which adds N- acetylgalactosamine to the terminal galactose of the H antigen, to create the A antigen (Ahmed, 2007). The B gene encodes D galactosyl transferase which adds D-galactose to the ternminal glactose of the H antigen to create B antigen. The O antigen doesnot produce a

Under the fisher system for nomenclature, each Rh haplotype is given a code. The most common genotypes the only individuals who area Rhd negative are those with the genotype dce/dce and these consists of 15% of Caucasians (Ahmed, 2007). The Individuals who are Rhd negative do not have normally have antibodies to the D antigen. However, they can become sensitised if transfused with blood from an Rh-positive individual. Rh antibodies must be stimulated by presentation of alien red cells to a subject’s immune system. The most common anti Rh antibody identifies the D molecule and is an IgG, and so has the ability to cross the placenta and attack the foetus therefore causing Haemolytic disease of the new-born (HDN) (Blann and Ahmed, n.d.) . In the early 1970s, anti-D was the most common cause of (HDN) It is serious disease which only occurs in a woman who are RhD negative and unless if the foetus is RhD is positive. The treatment to prevent Rh sensitization has been available since the 1970s, which has reduced the incidence of HDN due to RhD sensitization. The treatment involves the “intramuscular injection of at least 500 IU of anti-D immunoglobulin within 72 hours of the birth of a RhD positive baby” (Ahmed,