Eureka!! Blood groups

Blood transfusions are an essential and often life saving procedure, 1 in 20 people will need to be given blood at one time in their life. But until the discovery of human blood groups, the transfer of blood and its components was often fatal.

Blood is composed of plasma, which contains salts and proteins, and several cell types. These include white blood cells to fight infection, and platelets that cause the blood to clot following injury. The most abundant cells in human blood are red blood cells, which carry oxygen to all the tissues in the body.

The average adult human has a blood volume of around 4 to 6 litres and significant blood loss (around 30% of total blood) can have devastating consequences. In these situations a blood transfusion is necessary, but other conditions such as severe anaemia and thrombocytopenia (a lack of platelets) may also require transfusion of blood components. Such procedures may be carried out much more safely today thanks to the development of the ABO blood group system. The blood groups A, B and O were discovered in 1901 by Austrian biologist Karl Landsteiner, who won the Nobel Prize in Physiology or Medicine in 1930. A year later the fourth group, AB, was described. There are now hundreds of minor blood groups that have been identified, but the ABO system remains the most important.    

Blood groups are hereditary, and refer to the presence or absence of antigens on the surface of red blood cells. Antigens are molecules that are recognised by the immune system; individuals may have only A or B antigens, or both, or neither, to give blood types A, B, AB and O, respectively. The Rhesus (Rh) factor blood group system must also be considered in transfusion medicine. Individuals are classified as Rh negative or positive depending on the absence or presence of the main Rh antigen.

Transfusion problems arise when incompatible blood types are mixed, and antibodies (proteins that recognise foreign objects) in the blood plasma bind to their respective antigen on the donor red blood cells. What follows is an immune response which causes red blood cells to crack and release toxic contents.

The initial discoveries of blood groups over a century ago have allowed the field of transfusion medicine to develop, saving millions of lives, and may possibly lead to the production of artificial blood in the future.