Blood Groups

 

Like other cells in the body, red blood cells have complex molecules of carbohydrate polymers and proteins that give the cells their antigenicity.
The corollary to the above is the fact that antibodies exist that act against these antigens
In the presence of the particular antibodies, red cells agglutinate.
In contrast to clotting, agglutinated blood remains fluid, though the red cells clump together.
Though the large number of different antigens result in tens of different blood group systems, in practice there are only two, clinically important blood group systems. These are
	The ABO system.
	The Rhesus Factor System.