Final answer:
The Rh (Rhesus) blood group system is vital in clinical settings, particularly for blood transfusions. Its most crucial antigen is the D antigen, determining if an individual is Rh positive or negative and their compatibility with Rh+ or Rh- blood.
Step-by-step explanation:
The major group of erythrocytes antigens that are of extreme clinical importance is the Rh (Rhesus) blood group system. Of the antigens within this system, the most significant is the D antigen. Individuals with the D antigen are classified as Rh-positive (Rh+), which indicates they can safely receive transfusions of Rh+ or Rh- blood. However, those who lack the D antigen (Rh-) are limited to transfusions with Rh- blood to avoid immunological complications such as acute hemolytic transfusion reactions.
This system is second in importance only to the ABO blood group system when it comes to blood transfusions. The Rh system is named after the rhesus macaque, where the Rh factor was first discovered, and it involves more than 50 specificities. The presence of the D antigen, in particular, influences how blood transfusions are conducted and has implications for conditions such as hemolytic disease of the newborn (HDN).