How blood group is determined?
Our blood is composed of RBC's (Erythrocytes), WBC's (Leucocytes), Platelets (Thrombocytes) and Plasma. RBC is the only one which is used to define blood group. In ABO system, our blood group is defined by the presence or absence of Antigen 'A' and Antigen 'B' on the surface of RBC's. Antigens are the molecule that are present on the surface which stimulates immune response.
Apart from the antigen, antibodies are present in the plasma which fights against specific antigens. For Antigen 'A', Antibody 'B' will be present in plasma and for Antigen 'B', Antibody 'A' will be present in the plasma.
Antibody 'A' will fight against Antigen 'A' and Antibody 'B' will fight against Antigen 'B'.
If Antigen 'A' is present on the surface of RBC's then the blood group of the person will be 'A' blood group and if Antigen 'B' is present on the surface of RBC's then blood group of the person will be 'B' blood group.
In some individuals, blood group 'AB' and blood group 'O' are also found. If both Antigen 'A' and Antigen 'B' are present on the surface of RBC's then blood group of that person will be 'AB' blood group and no antibodies will be present in the plasma. If none of the Antigen are present (Antigen are absent) then blood group of the person will be 'O' blood group and they contains both Antibodies 'A' and 'B' will be present in the plasma.
Blood group table
Blood compatibility
If blood (RBC's) of blood group 'A' is donated to the person of blood group 'B' then the antibodies of the blood group 'B' will destroy the RBC's of blood group 'A'. Similarly, if blood of blood group 'B' is donated to the person of blood group 'A' then the antibodies of blood group 'A' will destroy the RBC's of blood group 'B'.
Universal donor
Blood group 'O' is called as universal donor because it can be donate to blood group of any type. The reason behind this is that RBC's of blood group 'O' don't have antigens on their surface, so no antibodies will fight against them.
Universal receptor
Blood group 'AB' is called as universal acceptor because it can accept blood from blood group of any type. The reason behind this is that plasma of blood group 'AB' don't have antibodies that can fight against antigens, so it can accept blood from any any type of blood group.
Rhesus factor (Rh)
Another factor which defines the blood group is Rhesus factor. It gives positive (+ve) or negative (-ve) to blood group. It is also an protein (antigen) found on the surface of RBC's. The Rhesus (Rh) protein is named after the monkey - Rhesus monkey, which also carries the gene, and the protein that lives on the surface of their RBC's. This Rh protein is also often called the D antigen.
RBC's which has Rh antigen on their surface are Rh positive (Rh +ve) and which don't has are Rh negative (Rh -ve).
e.g. If RBC of blood group 'B' contains Rh antigen then the blood group is called B positive (B +ve) blood group and if RBC lacks Rh antigen then it is called B negative (B -ve) blood group.
During blood transfusion, anyone who is Rh positive can receive blood from someone who is Rh negative, but those with negative blood types cannot receive from anyone with a positive blood type.
Meanings
1. Erythrocytes: A red blood cells (RBC's) which contains haemoglobin which gives red colour to blood and transports oxygen and CO2
2. Leucocytes: A colourless cell which circulates in the blood and has important function in immune response.
3. Thrombocytes: A small colourless disc-shaped cells found in blood and involved in clotting of blood.
4. Plasma: The colourless or milky fluid part of the blood.
5. Antigen: The foreign substance which stimulate immune response in the body.
6. Antibody: A blood protein produced in response to antigen and fight against them.