Question

Write a note on antigens on blood cells.

Answer 1

There are several known antigens on the surface of human red blood cells. These antigens give rise to different blood groups.

ABO Blood Groups:

The A, B, and O blood groups were discovered by Karl Landsteiner in 1900.

He found two antigens or agglutinogens on the surface of human red blood cells and named them antigen A and antigen B. He also noticed the corresponding antibodies or agglutinins in the serum called ‘a’ and ‘b’.

Blood group	Genotype	An antigen on the Surface of RBC	Antibody in Serum	Can donate blood to	Can receive blood from
A	IA IA or IA IO	A	Antibody b	A, AB	A, O
B	IB IB or IB IO	B	Antibody a	B, AB	B, O
AB (universal acceptor)	IA IB	A and B	Nil	AB	A, B, AB, O
O (universal donor)	IO IO	Nil	Both Antibody a and Antibody b	A, B, AB, O	O

In the ABO system, the blood groups are determined by the presence or absence of antigen A and antigen B. The blood group of a person is classified into four groups A, B, AB, and O.

Blood group A: Individuals, with blood group ‘A’, has the antigen A on the surface of their red blood cells (RBCs) and antibody ‘b’ in their plasma.

Blood group B: Individuals with blood group ‘B’ have the antigen B on the surface of their RBCs and antibody ‘a’ in their plasma.

Blood group AB: Individuals with blood group ‘AB’ have both antigens A and B on the surface of their RBCs and no antibodies in their plasma.

Blood group O: Individuals with blood group ‘O’ lack both antigens A and B on the surface of their RBCs and show the presence of both ‘a’ and ‘b’ antibodies in their plasma.

Rh factor: Rh – factor is an antigenic protein present on the surface of the red blood cells in human beings.