An update on the RHAG blood group system

Area of Science:

• Immunohematology
• Genetics
• Blood group serology

Background:

• The Rh-associated glycoprotein (RhAG) blood group system (ISBT 030) is crucial for understanding red blood cell surface antigens.
• Previous knowledge included high-prevalence antigens DSLK (RHAG3) and other RhAG-related antigens.

Purpose of the Study:

• To report the addition of three new low-prevalence antigens to the RhAG blood group system.
• To characterize these new antigens and their genetic basis.
• To investigate their clinical significance, particularly in hemolytic disease of the fetus and newborn.

Main Methods:

• Serological characterization of new antigens.
• Genetic analysis of RHAG mutations.
• Clinical data review for implicated cases of hemolytic disease of the fetus and newborn.

Main Results:

• Three new low-prevalence antigens (RHAG5, RHAG6, RHAG7) have been identified on RhAG.
• RHAG5 is antithetical to the high-prevalence antigen DSLK (RHAG3).
• RHAG6 and RHAG7 result from rare missense RHAG mutations affecting externally located amino acids.
• All three new antigens are implicated in hemolytic disease of the fetus and newborn.
• The RHAG system now comprises six antigens (two high, four low prevalence) with one antithetical pair.
• RHAG4 has been rendered obsolete.

Conclusions:

• The RHAG blood group system has expanded with the addition of three clinically significant low-prevalence antigens.
• These findings enhance the characterization of the RHAG system and its role in transfusion medicine and pregnancy.
• Further research into these antigens may improve diagnostic and management strategies for hemolytic disease of the fetus and newborn.