Blood is the only fluid connective tissue with a matrix called the plasma. Blood consists of many cells like platelets, red blood cells, and so on, in varying quantities, depending on their requirement. Blood types are determined by antigens which are tiny molecules found on the surface of red blood cells or erythrocytes. We usually inherit our blood from our parents but, sometimes, we can also inherit from our relatives. Inheritance of blood group follows Mendelian patterns, in essence, they are the product of a single gene.
There are four types of blood- A, B, O and AB. These blood groups are found to be either RhD-positive or RhD-negative. Here, RhD stands for Rhesus Factor D and it refers to the protein found on the surface of the red blood cells (RBCs) which shows the compatibility of the mother’s cell with that of the offspring’s. It is also called an RhD antigen.
This system of distinguishing blood types has been called the ABO system and was discovered by Karl Landsteiner in 1901. According to him, there are three types of blood alleles (multiple versions of a DNA sequence); A, B, and O. A and B alleles are codominant, that is, they are equally dominant while allele O is recessive. These give rise to the blood groups- A, B, O, and AB. The antigens change based on the allele they possess. They can be:
Allele O does not have any antigens.
Allele A and B form type A and B antigens respectively.
The RhD system determines the presence or absence of a particular antigen on the surface of the red blood cells. The presence makes the blood group “positive” while absence makes it “negative”. The absence of this antigen does not pose a life-threatening risk to an individual’s life.
Blood compatibility is something that has to be considered during medical procedures. Transfusion of non-compatible blood groups, ABO and RhD systems, can be fatal and can cause an “acute hemolytic transfusion reaction” in which hemolysis is observed. In hemolysis, rupture or destruction of red blood cells or erythrocytes is observed. Therefore, it is necessary to know the blood type of the patient before performing such transfusions.
Type O blood is compatible with all types and hence, is called as a universal donor. However, type O can receive only type O blood. Type AB can receive all blood types and is therefore called a universal acceptor. If you have type A blood, you can only receive type A or O blood. Similarly, you can receive type B or O blood if you have type B blood.
Considering all of this, it is heavily appreciated that people volunteer to donate blood and save lives. Donating blood is a kind act of generosity and you can donate it at your nearest blood bank. A single blood donation can save up to three lives.
Written By: Vinti Majethia
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