Human Rh Blood Group, D Antigen (RHD) Protein

Background

RHD (Rh blood group D antigen), encoded by the RHD gene, is a major component of the Rh blood group system, one of the most clinically significant blood group systems in humans. The Rh system includes a range of antigens, but the D antigen is the most important for its role in blood transfusion compatibility, pregnancy, and disease. The Rh system is widely recognized in transfusion medicine, where the presence or absence of the D antigen determines whether an individual is classified as Rh-positive (Rh+) or Rh-negative (Rh-). The Rh system, particularly the D antigen, plays a crucial role in immune reactions, alloimmunization, and hemolytic disease of the newborn (HDN). The RHD gene is located on chromosome 1 and is closely linked to the RHCE gene, which encodes other Rh antigens, particularly C and E. The Rh proteins, including the D antigen, are integral membrane proteins that span the cell membrane and play an essential role in the transportation of ions and gases across the cell membrane, especially in erythrocytes (red blood cells). The RHD gene codes for the RhD protein, and its expression is key to determining whether an individual expresses the RhD antigen on the surface of their erythrocytes.