Blood Groups

Blood Groups

The concept of blood grouping was developed by Karl Landsteiner (1900). He identified blood groups A, B and O. AB blood group was recognized by Decastello and Steini (1902).

Human blood contains certain specific substances called agglutinogens or antigens (Ag) and agglutinins or antibodies (Ab). Antigens are found on the membrane surface of RBC. Antibodies are present in blood plasma. Based on the presence or absence of antigen and antibodies human blood group is classified into four groups called A, B, AB and O. An individual has one of the four blood groups.

(i) ‘A’ group individuals: Antigen A is present on the surface of RBC and antibody b (anti-b) is present in the plasma.

(ii) ‘B’ group individuals: Antigen B is present on the surface of RBC and antibody a (anti - a) is present in the plasma.

(iii) ‘AB’ group individuals: Antigens A and B are present on the surface of RBC and both the antibodies are absent in the plasma.

(iv) ‘O’ group individuals: Antigen A or B are absent on the surface of RBC. However, the plasma contains both the antibodies a and b (anti a and b).

Blood donation

In blood transfusion one must consider the antigen and antibody compatibility (matching) between the donor and the person receiving blood (recipient). When an individual receives a mismatched blood group from the donor agglutination (clumping) of blood occurs in the body which leads to death.

Persons with ‘AB’ blood group are called ‘Universal Recipient’ as they can receive blood from persons with any blood group.

Persons with ‘ O’ blood group are called ‘Universal Donor’ as they can donate blood to persons with any blood group.

Rh factor

Rh factor was discovered by Landsteiner and Wiener in 1940 in Rhesus monkey. The surface of RBC contains the antigen for Rh factor. Rh⁺ ( positive) persons have Rh antigen on the surface of RBC while, Rh^– (negative) persons do not have Rh antigen on the surface of RBC. Antibodies developed against this Rh antigen is called Rh antibodies.