Rhesus factor D antigen (RhD antigen (also commonly referred to as RhD or D antigen))

The Rhesus factor D antigen, also known as RhD, is a transmembrane protein found on human red blood cell surfaces. It is encoded by the RHD gene located on chromosome 1p36-p34. The presence or absence of this protein determines whether an individual’s blood type is classified as “Rh-positive” or “Rh-negative.” The structure suggests it may be part of an ion channel complex involved with ammonia transport; however, its primary clinical significance lies in its role as one of the most immunogenic human erythrocyte antigens. Antibodies against this molecule can cause severe complications such as hemolytic disease of the newborn when there’s incompatibility between mother and fetus, or delayed hemolytic reactions after incompatible transfusions. Its high genetic variability poses challenges for precise matching but makes it central to safe practices in both obstetric care and transfusion medicine.

Other names

RhDCD240DRh blood group D antigenRh polypeptide 1 (RhPI)Cluster of differentiation 240D (CD240D)RHD proteinRH30RH4RHIIRHCED

Anti-D immunoglobulin binds circulating fetal Rh-positive red cells in maternal circulation, preventing maternal immune sensitization and subsequent antibody production against the D antigen.