APIB223886221 - CME/CMLE - Overview of Rh System-APIB223886221

APIB223886221 - Educational Activity

Pdf Summary

The Rh blood group system is one of the most significant in transfusion medicine after the ABO system, with 55 antigens primarily located on RhD and RhCE proteins. The five primary antigens—D, C, c, E, and e—are crucial due to their immunogenicity, especially the D antigen.<br /><br />Rh antibodies are elicited through exposure to foreign antigens via transfusion or pregnancy, forming primarily IgG antibodies. These antibodies can cause hemolytic transfusion reactions (HTRs) and hemolytic disease of the fetus and newborn (HDFN). To mitigate these risks, Rh-negative individuals or those with altered D-antigen expression should receive Rh-negative blood products. Rh immune globulin (RhIG) is used to prevent HDFN in Rh-negative pregnant women exposed to the D antigen.<br /><br />The Rh antigens are encoded by the RHD and RHCE genes on chromosome 1 and require the RHAG gene on chromosome 6 for expression. While the majority of populations have a high percentage of Rh-positive individuals, altered expressions like weak D and partial D phenotypes can occur due to amino acid changes affecting antigen presentation. For instance, weak D phenotype individuals have a reduced but complete set of D antigens, often not forming antibodies against D, while partial D individuals lack some D epitopes and can form alloanti-D.<br /><br />Additional complexities include the Del phenotype, common in Asians, where D antigen levels are so low they escape routine testing. Rh-negative phenotypes are most often due to the deletion of the RHD gene.<br /><br />The other Rh antibodies—anti-C, anti-c, anti-E, and anti-e—are also critical. They display variable immunogenicity and can cause HTRs and HDFN. For instance, anti-C and anti-c can cause severe reactions, necessitating antigen-negative transfusions.<br /><br />Variants arise frequently, with higher prevalence in African ancestries. Continual advancements in molecular techniques aid in the detection and management of these variations, thereby improving transfusion safety and outcomes for at-risk populations.

Keywords

Rh blood group

transfusion medicine

RhD antigen

RhCE proteins

immunogenicity

hemolytic disease

Rh immune globulin

RHD gene

RHAG gene

molecular techniques