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).

Blood and blood products are collected as whole blood from donors in various anticoagulants. The blood and blood products which are used for transfusion are whole blood, packed red blood cells (PRBCs), platelet concentrates, fresh frozen plasma (FFP), cryoprecipitate, and plasma derivatives. Plasma derivatives are also used for transfusion such as albumin, intravenous immunoglobulin, anti-thrombin, and coagulation factor concentrates. Plasma derivatives are generally collected from several donors and pooled together and infectious organisms are removed by treating.

Separation of blood components from whole blood:

Blood is collected as whole blood of 450 ml (one unit of blood) in various anticoagulants. The whole blood is then processed to produce blood various blood components mentioned above. Most commonly blood is transfused as whole blood. To get blood components, whole blood is first separated by slow centrifugation into PRBCs and platelet rich/concentrated plasma.