BLOOD GROUP SYSTEMS

In 1901 scientists discovered the fi rst blood groups— those of the ABO system. Since then, the realization that red blood cells possess proteins that can be used to classify them into various blood groups has revolutionized medicine. Prior to this knowledge, blood transfusions were dangerous and had unpredictable outcomes, with some patients experiencing severe reactions and others faring well for unknown reasons. Today, however, because blood group proteins on red cells can be identified accurately and because donor blood is screened for the presence of potentially dangerous infectious organisms, blood transfusions are relatively safe and effective

procedures. More than 20 blood group systems have been identified, each of which is genetically distinct. In fact, investigation of the genetic characteristics of blood groups has played a crucial role in improving knowledge of the underlying physiological functions of blood group proteins. This in turn led to the discovery that some of these substances have important roles in protection against diseases such as malaria. In the 20th century, some studies of blood groups focused solely on elucidating the incidence of blood group antigens in various populations worldwide. As a result, today there is extensive information available about the genetic frequency and prevalence of certain blood groups in populations of differing geographic, racial, or ethnic backgrounds. Thus, many blood groups serve as important genetic markers, providing key information about human populations and their evolution.

The classification of blood is based on inherited differences (polymorphisms) in antigens on the surfaces of the red blood cells (erythrocytes). Inherited differences of white blood cells (leukocytes), platelets (thrombocytes), and plasma proteins also constitute blood groups.

Reference:

Rogers, Kara. 2010. Blood: Physiology and Circulation. New York: Britannica Educational Publishing.