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