Classification of blood groups
Though Karl Landsteiner, an Austrian physician, discovers the first three human blood groups (A, B,O) in 1901, it was only in 1939-40 that the Rh blood group system was discovered by Karl Landsteiner, Alexander Wiener, Philip Levine and R.E. Stetson. This was based on the presence / absence of various antigens (A and B) and the presence / absence of the Rhesus antigen (RH factor) on red cells. This paved the way for classifying the human into major blood groups as A+ve, A-ve, B+ve, B-ve, AB+ve, AB-ve, O+ve and O-ve.
Distribution of blood groups:
The most common blood group is O positive and the rarest blood group is AB negative.
It is very important to have a back up of the rare blood group blood in any blood bank because it may be difficult to get a fresh donor in an emergency.
Antigens and antibodies of blood groups
The most important factor which determines compatibility of blood is the presence of antibodies which act against the antigens A, B and Rh and identification of antibodies which react to these antigens.
Blood Group Compatibilty Thus as we saw above, each blood group can receive blood only from specific blood groups as given in the table
As you see here, the O-ve blood can be given to all blood groups making it a Universal Donor Blood group. But an O-ve person can receive only O-ve blood.
AB+ve can receive blood from any other blood group making it the Universal Receipient
Blood group compatibility is not just important in transfusion matters, but also in cases of Rh-ve mothers pregnant with a Rh+ve baby.