Blood groups

Blood groups are a classification of the blood in the human body based on the presence or absence of antigens on the surface of red blood cells. These antigens can be proteins, carbohydrates, glycoproteins, or glycolipids. The blood group system is important in blood transfusion and pregnancy, as some blood groups are incompatible with others.

History

The discovery of blood groups was made by the Austrian scientist Karl Landsteiner in 1901. He identified the A, B and O blood groups, and later, in collaboration with Alexander S. Wiener, discovered the Rh factor, leading to the identification of the most common blood group system, the ABO blood group system.

ABO Blood Group System

The ABO blood group system is the most important blood group system in human blood transfusion. The ABO blood group system includes four different blood groups: A, B, AB, and O. Each group is characterized by a specific set of antigens on the surface of the red blood cells.

Group A

Individuals with blood group A have A antigens on the surface of their red blood cells and anti-B antibodies in their plasma.

Group B

Individuals with blood group B have B antigens and anti-A antibodies in their plasma.

Group AB

Individuals with blood group AB have both A and B antigens on their red blood cells and no antibodies in their plasma. This group is considered the universal recipient in blood transfusion.

Group O

Individuals with blood group O have neither A nor B antigens on their red blood cells but have both anti-A and anti-B antibodies in their plasma. This group is considered the universal donor in blood transfusion.

Rh Blood Group System

The Rh blood group system is the second most important blood group system, after the ABO blood group system. It was named after the Rhesus monkey, in which it was first discovered. The most significant antigen in this system is the D antigen. Individuals who have the D antigen are referred to as Rh positive, while those who lack it are referred to as Rh negative.

Other Blood Group Systems

In addition to the ABO and Rh blood group systems, there are over 30 other recognized blood group systems, including the Kell, Duffy, Kidd, and MNS systems. These are less commonly considered in blood transfusion, but can be important in certain clinical situations.

Importance in Medicine

The correct identification of a patient's blood group is crucial in blood transfusion and organ transplantation. Mismatched blood can cause a severe and potentially fatal reaction. In pregnancy, the blood group can also be important, as an Rh negative mother can develop antibodies against an Rh positive baby, leading to hemolytic disease of the newborn.