ABO blood group system

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By Fatima Farooq

THE CLASSIFICATION of human blood is based on the inherited properties of red blood cells (erythrocytes) as determined by the presence or absence of the antigens A and B, which are carried on the surface of the red cells. Persons may thus have type A, type B, type O, or type AB blood. The A, B, and O blood groups were first identified by Austrian immunologist Karl Landsteiner in 1901.
ABO is the most important blood group system in human blood transfusion. It is a series of antigens exhibiting similar physical and serological characteristics and inherited according to a specific pattern. In this system, all blood belongs to one of four major groups. A, B, AB or O. Type AB+ is the universal recipient, whereas type AB- is not. A -, A+, B-, B+, AB-, AB+,O-or O+ individuals can all receive blood from donors of type O- blood. An individual with type O- blood is known as universal donor.
As our blood is composed of cells suspended in liquid, the liquid portion of the blood is the plasma. In Plasma there are three types of cells normally in suspended form – red cells, white cells and platelets. Red blood cells (RBC) carry O2. White cells fight against infections/diseases and Platelets stop bleeding in injuries. Specific alleles (alternative form of a gene that is located at a specific position on a specific chromosome) are responsible to control the four types of classical blood groups. The alleles are IA, IB and i. As only two are possible in an individual there are four blood groups that will have the following combinations of alleles.
ABO antigens are glycolipid in nature. Means they are oligo saccharides attached directly to lipids on red cell membrane. Besides, their presence on red blood cells soluble antigen can be present in plasma, saliva and other secretions. These antigens are also expressed on tissues other than red cells.
Moreover, the ABO blood groups system is also present in some other animals. For example: One blood group with three types has been described in cats, whereas multiple blood groups have been described in the dog. Only rudimentary knowledge exists regarding pet bird blood groups, and, to date, the ferret appears to be unique because no blood groups have been described.
Understanding the issues related to blood groups and blood group antibodies in companion animals will also benefit those using these species as research models for human diseases.
The writer is a Biotechnology student at Abdul Wali Khan University, Mardan.


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