RHD encodes the Rh blood group D antigen, a membrane protein that functions as an ammonium transporter in erythrocytes. The protein likely forms oligomeric complexes with transport or channel activity in the erythrocyte membrane 1. RHD expression is dependent on the presence of RHAG (Rh-associated glycoprotein), as RhD antigen cannot be expressed alone and requires transgenic human RhAG for proper membrane localization 2. The primary clinical significance of RHD relates to blood group incompatibility and hemolytic disease of the fetus and newborn (HDFN). Anti-RhD alloimmunization occurs when RhD-negative individuals are exposed to RhD-positive blood, leading to antibody production 2. Serological weak D phenotypes, occurring in 0.2-1% of routine blood typings, require RHD genotyping for proper management, with most Caucasian weak D types (1, 2, or 3) safely manageable as RhD-positive 3. RHD genotyping has become essential for identifying partial D phenotypes and guiding anti-D prophylaxis in pregnancy 1. The development of transgenic mouse models expressing human RhAG and RhD proteins represents an important advancement for studying RhD alloimmunization mechanisms and HDFN pathogenesis 2.