Human blood types, blood antigens and antibodies, how to do blood grouping and more

REDMEDBD
REDMEDBD
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Published 2020-09-17
Antigens are molecules those which are considered as foreign substances that can initiate immune response in human body. Antibodies are protein molecules those which are produced by the body to neutralize the antigens. The word “agglutinate” means to adhere or to stick with something. When we talk about blood grouping we use the term agglutinogen instead of antigen and agglutinin instead of antibody. When agglutinogen and agglutinin react with each other or stick to each other we call it the agglutination reaction. This is important because the whole blood grouping system is dependent on it.


Human body has 3 types of cells in the blood. Those are namely RBC, WBC and platelets. On the surface of the RBC we find 2 types of agglutinogens. They are called agglutinogen A and agglutinogen B. If a person has agglutinogen A on the surface of the RBC then we say his blood group is A. If a person has agglutinogen B on the surface of the RBC then we say his blood group is B. There are also people who have both of the antigens on the surface of their RBC and we say their blood group is AB. If a person has none of the antigens on the surface of the RBC then we call his blood group as “O”. This is why this blood grouping system is called the ABO blood grouping system. This blood grouping system was developed by an Austrian immunologist Named Karl Landsteiner in 1901.



If we transfuse a person with wrong blood group then he will have a severe post blood transfusion reaction, his blood will form clots and he may die from the reaction as well.

Each of the agglutonogen A & B has their corresponding anti-A and anti- B agglutinins. The presence of anti-A and anti-B in the blood depends on the presence of the agglutinogen A and agglutinogen B on the red blood cell surface. When agglutinogen A is present on the red blood cell surface the corresponding anti-A antibody will be absent in the blood but the Anti-B antibody will be present in the blood. And when agglutinogen B is present the corresponding anti-B antibody will be absent in the blood but anti-A antibody will be present in the blood.
When both of the antigens are absent then both anti-A and anti-B antibody will be present in the blood. This is why a person with blood group “A” has agglutinogen A and anti – B in the blood. A person with blood group “B” has agglutinogen B and anti-A antibody in the blood. A person with blood group “AB” has agglutinogen A & B but no anti-A or anti-B. But a person with the blood group “O” has both the anti-A and anti-B antibodies in his blood. Now let’s imagine Jake has blood group A & Paul has blood group B. If Paul donates blood to Jake then the following will happen. Paul’s B antigen is unknown to Jake so the anti-B antibody in Jake’s blood will recognize Paul’s B antigen as a foreign substance and an agglutination reaction will happen in Jake’s body. Which will result in the formation of blood clots in Jake’s body & he will probably die from multi-organ failure and excessive destruction of red blood cells. For the same reason Jake cannot also donate blood to Paul.

Universal donor
Remember we talked about the blood group “O” which has neither antigen A nor antigen B on the cell surface of the red blood cell? So what will happen if we transfuse “O” blood to Jake and Paul? Turns out, due to the absence of the antigens in the “O” blood it will not produce any kind of reactions in their bodies. “O” blood can also be transfused to any person with blood group “AB” and of course to the person with same blood group “O”. That is why the blood group “O” is called the universal donor.


Universal receiver
Let’s imagine Lucy has blood group “AB”. Can Jake and Paul donate blood to Lucy? Yes, they can. Because Lucy has both of the antigens in her blood so it doesn’t matter either Jake or Paul donates blood to her. In none of the cases she will develop antibodies. She can also receive blood from “O” and another person with “AB” blood group. This is why blood group “AB” is called the universal receiver.



Rh blood grouping system
After 36 years of the discovery of ABO blood grouping system Karl Landsteiner and Alexander S. Wiener in 1937 observed another type of antigen on the RBC. It was called the antigen “D”. Which has some similarities with an antigen found in Rhesus monkey’s blood cells. Hence the term Rhesus factor was born. And ultimately the blood grouping system was named Rh blood grouping system. If a person has the antigen D on the surface of the RBC we call him positive and if there is no antigen D we call him negative. For an example, Jake has ABO – “A” and Rh positive blood. This can also be called “A” positive blood. This is important to remember Rh negative people doesn’t have anti-D antibodies in their blood like the ABO system. So Rh negative means the person has neither D antigens nor the anti-D antibodies in their blood.


#bloodGrouping #Rh_typing #explanation
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