What Is Immunohematology

Most people are aware of three blood group “antigens”, A, B, and Rh, in two blood group systems, ABO and Rh. In fact there are over 300 blood group antigens in over 30 blood group systems. When individuals are exposed to the red blood cells (RBCs) of other people by transfusion or pregnancy (RBCs of the fetus) their immune system can make “antibodies” against the blood groups that are foreign to their system. That process is the same one that makes us immune to bacteria and viruses. In the case of RBCs such immunity causes us to be “incompatible” with the foreign blood group antigens and the RBCs that bear them, and most often to destroy the incompatible RBCs, sometimes with severe reactions in the recipient.

In many countries blood banks deal with compatibility problems by detecting antibodies before transfusion, identifying the blood group against which they’re directed, and then providing RBCs that lack the offending blood group. This is the science of “immunohematology”. However, blood banks in many low or even middle income countries lack the technology to identify blood group antibodies. This includes many of the blood banks in South Asia. Every day blood bankers in developing countries transfuse RBCs that they know are incompatible, and they do this with dread that the patient will experience serious complications. Hear firsthand experience here.

Patients can also make antibodies against their own RBCs. If these antibodies are able to destroy RBCs the patient can become anemic and may die. In pregnant women blood group antibodies may destroy the RBCs of the fetus or of the baby soon after it is born. This problem is called Hemolytic Disease of the Fetus and Newborn (HDFN). In the 1950’s and 1960’s HDFN was the most common cause of death of fetuses and newborn babies in the United States.

In order to identify and properly treat these problems blood banks must have the technology to identify blood group antibodies.

Blood group antibody identification becomes an issue when the medical system is sophisticated enough to frequently need and use transfusions. For example, multiple transfusions are often needed to support patients who are being treated with chemotherapy for cancer. Patients who get multiple transfusions frequently make blood group antibodies. And more and more patients in developing countries are receiving sophisticated cancer chemotherapy. The same is true for cardiac surgery, organ transplantation, and a host of other advanced procedures. So Indian blood bankers identify learning to perform blood group antibody identification as a priority.