Contemporary Knowledge of the Rh System

Overview

The Rh system belongs along with the AB0 system to the clinically most important systems of bloodgroups. The RhD antigen is the most immunogenic structure of the red blood cell membrane. The Rhsystem contains the largest amount of antigens of all blood group systems. Recent years provided manynew findings on its biochemical and molecular genetic background. Antigens of the Rh system are onRh proteins, which are part of the Rh complex of the erythrocyte membrane. There are two very similarRh proteins – RhD and RhCcEe, coded by two related genes – RHD and RHCE. While RhD positivityimplies the presence of RhD protein and RhD negativity its absence, the majority of the other antigensof the Rh system is determined by much smaller differences of individual Rh proteins (e.g. the allelicpair E/e differs only in one amino acid). Rh proteins form in the membrane tetrameric complexes withRh glycoprotein. In the phenotype and clinical syndrome Rhnull the formation of these tetramers isimpossible due to mutations of the gene for Rh glycoprotein or Rh protein and on the red blood cell noRh antigens are found. Other mutations causing incomplete blocking of complex formation are thecause of poorly expressed Rh antigens. If mutations and reconstructions of RH genes cause a changein the immunogenic part of Rh proteins, Rh variants develop which are characterized by the absenceof certain epitopes and the possibility to form anti-D antibodies against normal Rh antigens. At presentwe differentiate by means of monoclonal antibodies more than 30 RhD epitopes, at the molecular levelalready more than 30 alleles for D variants were described and 20 alleles for weak D antigens.Key words: Rh system, Rh complex, RHD, RHCE and RHAG genes, RhD and RhCcEe proteins, RhAGglycoprotein, Rh variants, weak antigens

Key words:
Rh system, Rh complex, RHD, RHCE and RHAG genes, RhD and RhCcEe proteins, RhAG