While growing up, I used to wonder why we carried out of these blood test to determine what my blood group and genotype was, and even at that young age, they usually tell us that it was important to know this information as your life one day could depend on it.
So I set out to understand the significance of the so-called blood group and Genotype, and what better way to do that than Joining the Medical profession as a Medical Laboratory Scientist and currently a student DOCTOR.
Human blood is made up of two components physically
1) Blood cells
2) Serum
The blood cells are majorly three, the red blood cells, the white blood cells, and the platelets while the serum contains all the other nutrients, minerals, proteins, and so on.
The Blood group antigens are found on the surface of the red blood cells and they find their major significance in Blood transfusion, while the genotype is found in the pigment that makes the blood red, called the hemoglobin.
Blood group
While there are so many blood grouping systems such as ABO, Rhesus, Lewis, Duffy, and a host of others, the ABO and Rhesus blood group systems are the most significant to humans especially in Blood transfusion sciences. They, to a great extent, determine the compatibility of an individual blood group to another.
We've all heard the cliche that blood group O- are universal donors while the Blood group AB+ are the universal recipient. It simply means that the blood group O+ can donate blood to any of the other blood groups while the blood group AB+ can receive blood from any of the blood groups.
But it's not that simple as it sounds, let me break it down.
There are four major ABO blood groups;
O
A
B
AB
For the Rhesus, which was discovered in a Rhesus monkey, hence the name Rhesus, there are just Rhesus Positive and Rhesus negative. So these four ABO blood groups could be Rhesus positive or Negative.
The idea of the Rhesus blood grouping was brought about when it was discovered that even though people of the same blood group could donate blood to each other, say A gives A, there were still instances when the blood, though of the same ABO blood group, weren't compactable and there were transfusion Reactions. Scientists wondered what could be the cause until the Rhesus system was discovered.
Hence we now have, combining the ABO blood group and the Rhesus, the following blood groups as seen in the photo below.
In summary, the ABO blood groups could be either Rhesus positive or Rhesus Negative.
We should first establish that any given ABO blood group can donate blood to itself. But there is a principle that may be confusing at first but would get easier to understand with time.
I would break down the principles as follows
1) Blood group O contains no antigen on the surface of the Red blood cell
2) Blood group A contains antigen A
3) Blood group B contains antigen B
4) Blood group AB contains both antigens A and B. Hence there are just two antigens in the ABO system, A and B.
5) Any of the blood groups could contain the Rhesus Antigen (positive) or not (Negative).
Now to know which blood groups could be compatible, it's a principle that
1) for every antigen a blood group has, it has the opposite antibody (antibodies are immunogenic substances produced in reaction to an antigen). Hence Blood group A has Antigen A and antibody B. The list as seen in the picture below.
2) An antigen would react to its antibody to produce an agglutination reaction, which in the case of a transfusion, a transfusion Reaction, hence, incompatible.
With this in mind, you can understand why blood group O+ is the universal donor because it has no Antigen, hence, it can donate to any of the blood groups without any Reaction, while blood group AB is the universal recipient, because it has no antigen and hence cannot react to any of the blood group blood donations.
Having said all these, it's important to note that compatibility testing in clinical laboratories are designed following the principles outlined above, with other technical and safety factors such as protein density, temperature, coombs reaction, incomplete antibodies, sensitization, and so on, which I would not go into, are put into consideration before saying that a donor's blood is compatible with that of the recipient.
So why is the concept of universal donor and recipient so important if there are complex and sophisticated methods to check compatibility?
In the case of an emergency, during wars and accidents when urgent blood is needed and it is little or no time to run any compatibility test, the Universal donor blood, blood group O- could be used as a remedy in that instant, to save the person's life.
So why blood group O- and not O+. Before I go into this, it's important to state that blood group O can only receive blood from blood group O persons because they have both antibodies and hence, any other blood group which has an antigen would react to it.
As stated earlier, the Rhesus antigen, if given to a Rhesus negative person could sensitize the person's blood to begin to produce Rhesus antibodies. The reaction may not be visible at first, but maybe in subsequent transfusions, there may be serious reactions and implications, hence the use of Rhesus O- (Rhesus positive does not affect other Rhesus positive blood groups).
The significance of the Rhesus blood grouping system manifests more in Pregnancy involving a Rhesus Negative mother and a Rhesus positive father.
If the woman is a Rhesus Negative blood group of any of the ABO groups and the man is a Rhesus Positive of any of the blood groups, following Mendelian law of inheritance, the child is likely to be positive or Negative, if the child is Rhesus positive, then there would be no issue, but if the child is Negative, then there may be a serious problem.
Check out the next post which would explain the problem associated with the medical Situation above.
Thanks for reading.
