Antigenicity Causes Immune Reactions of Blood
When blood transfusions from one person to another were first attempted, immediate or delayed agglutination and hemolysis of the red blood cells often occurred, resulting in typical transfusion reac-tions that frequently led to death. Soon it was dis- covered that the bloods of different people have different antigenic and immune properties, so that antibodies in the plasma of one blood will react with anti-gens on the surfaces of the red cells of another blood type. If proper precau-tions are taken, one can determine ahead of time whether the antibodies and antigens present in the donor and recipient bloods will cause a transfusion reaction.
Multiplicity of Antigens in the Blood Cells. At least 30 commonly occurring antigensand hundreds of other rare antigens, each of which can at times cause antigen-antibody reactions, have been found in human blood cells, especially on the sur-faces of the cell membranes. Most of the antigens are weak and therefore are of importance principally for studying the inheritance of genes to establish parentage.
Two particular types of antigens are much more likely than the others to cause blood transfusion reactions. They are the O-A-Bsystem of antigens and the Rh system.