Which blood group antigen is associated with the Rh blood group system?

The blood group antigen associated with the Rh blood group system is the D antigen. The Rh system is one of the major blood group systems in humans and consists of several antigens; however, the D antigen is the most clinically significant. It is the presence or absence of this antigen on the surface of red blood cells that determines an individual's Rh status (Rh-positive or Rh-negative).

When a person is Rh-positive, they possess the D antigen, which is important during blood transfusions and pregnancy. If an Rh-negative individual is exposed to Rh-positive blood (for example, during a transfusion or if an Rh-positive fetus is carried by an Rh-negative mother), their immune system may produce antibodies against the D antigen, potentially leading to hemolytic reactions. Understanding the importance of the D antigen helps ensure safe blood transfusions and manage pregnancies involving Rh incompatibility.