If you have ever needed a blood transfusion, or donated blood, you probably would have been asked your blood type. In Gregory University Uturu, all new students, among other screening tests, must do their blood Group, genotype and Rhesus factor before admission. At times the students would come quoting their blood groups and genotype. We had always insisted that to make assurance doubly sure, we must reconfirm.
Prof Erica Wood of Monash University, Australia, had problems explaining to his first set of medical students in the late 18 century, who thought that all blood, looking at their colors, were the same. Some even suggested that in times of scarcity, even animal blood could be transfused to human beings. We now know there are different types of blood, called groups.
Transfusion between blood groups can be catastrophic, even deadly, so knowing the blood type of donors and recipients are of utmost importance. Our bodies contain trillions of red blood cells. Each is covered in an array of proteins and sugars inherited from our parents, which determine our blood Group. We can all be classified into group A, B, AB or O based on which sugars coat our red blood cells.
We are also classified as positive or negative based on whether our blood cells carry a protein called Rhesus D (RhD) antigen. These two blood group systems (ABO & Rh) give us the eight main blood types O-, O+, B-, B+, A-, A+, AB-, AB+. But there are also more than 300 different antigens – proteins and sugars that activate the immune system– expressed on red cells and 36 recognized blood group systems. And they are just the ones we know about.
Blood group was discovered in 1900, when a Physician Dr Karl Landsteiner’s experiment showed that some peoples’ red blood “reacted” with plasma samples from other people while others did not. This led to his describing the ABO system, the most important blood group system and the basis for safe modern transfusion. After receiving the 1930 Nobel Prize for Medicine for this work, Dr Landsteiner was experimenting with the blood of Rhesus monkeys, when he discovered what is now known as the RhD antigen.
Group O negative people are called “universal donors”, their red cells express neither group A nor B sugars, nor the RhD antigen, and so are unlikely to cause reaction in recipients. Emergency departments and some Ambulances carry a stock of O negative blood, because in an emergency this is the safest blood to transfuse a critically ill, bleeding and unconscious patient of unknown blood type.
One of the 36 blood group systems discovered is the “Duffy protein”, named after hemophiliac patient Mr Duffy. In 1950 he developed an antibody to what we know today as Duffy “a” antigen, to which he had been exposed by receiving blood transfusion. One of the known functions of the Duffy antigen is binding one type of malaria parasite Plasmodium vivax, which grants it entry into the red cell, where it can multiply and then cause cell to burst.
The red cell of people who lack Duffy antigens are more resistant to infection by this malaria parasite. More than two-thirds of people of African origin lack the Duffy antigens, whereas it is rare for people originating from Europe and Asia not to do so.
Many thousands of years ago, in Africa where the Plasmodium vivax – bearing mosquitoes flourished, people who lacked the Duffy antigens were resistant to the potentially fatal form of malaria and survived to parent future generations, passing on this particular resistance to their offspring. Hence Africans have herd immunity for malaria. Always be medically guided.
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