Blood and blood products transfusion can be life saving, but if not done appropriately and with appropriate precaution, blood transfusion can also cause problem to the recipient of the transfused blood. The complications that can occur due to blood transfusion includes, transmission of infectious agent (from donor to recipient), immunologically mediated adverse reactions (such as hemolysis, graft-versus-host reaction, anaphylactic reaction etc.), non-immunologically mediated adverse reactions such as hypothermia, fluid overload, electrolyte excess etc.

There are several infectious agents that can be transmitted through blood transfusion, but practically very rarely seen in clinical practice due to rigorous screening of blood for infectious agents before transfusion,

The transfusion medicine (blood and blood product transfusion) is basically the study of antigen and antibodies to RBCs (red blood cells). The two most important factors of blood transfusion are ABO antigens and antibodies and Rh system, most important being the ABO blood group antigen system and Rh system is the second most important factor in transfusion medicine. Other factors such as transmission of infectious agents, immunologic and non immunologic reaction of blood and blood product transfusion are secondary to ABO blood group antigen system and Rh system.

What is the importance of ABO antigens and antibodies?

The ABO antigen system is the most important in blood and blood product transfusion (also called transfusion medicine) and was first recognized in the year 1900. The ABO antigens are present in the plasma and other body fluids as glycoprotein, although the ABO antigens are carbohydrates and attached to lipids glycosphingolipids or proteins (glycoprotein). H substance is the precursor on which antigen A and antigen B are attached. Addition of N-acetylgalactosamine forms antigen A and addition of galactose produces antigen B. individuals who can not form H substance due to lack of the gene form Bombay phenotype (Bombay blood group).