Final answer:
Rh positive individuals have the Rh D antigen on their erythrocytes, leading to potential immune complications such as hemolytic disease of the newborn in future pregnancies if the mother is Rh negative and not treated with RhoGAM.
Step-by-step explanation:
The erythrocytes, or red blood cells, of an individual who is Rh positive (Rh+) carry the Rh D antigen. This antigen is a protein on the surface of red blood cells, and its presence signifies that a person is Rh positive. The Rh blood group system is significant in blood transfusions and pregnancy, as Rh negative individuals can form antibodies against Rh positive blood cells, leading to complications such as hemolytic disease of the newborn (HDN). HDN is typically only a problem during the second or subsequent pregnancies with an Rh positive fetus, as the initial exposure to Rh positive blood cells (which can occur during the first pregnancy or a blood transfusion) prompts the mother's immune system to produce antibodies. These antibodies, once formed, can cross the placenta in later pregnancies and attack the Rh positive red blood cells of a subsequent fetus, resulting in HDN unless interventions like RhoGAM are administered.