American Red Cross Allen Park, Michigan, United States
Background/Case Studies: The Rh blood group system has 52 recognized antigens located on two genes found on chromosome 1 known as RHD and RHCE. A single amino acid change can affect the expression of the protein and may result in the expression of a new epitope: thus, the RHCE gene has numerous variants. Two antigens in the Rh blood group system, V (Rh10) and VS (Rh20), are likely conformationally dependent antigens which require the presence of one of these types of changes, currently understood to be the RHCE*ce733C >G mutation. The objective of this study was to investigate the serological expression of the V and VS antigens on variant RHCE*ce alleles including RHCE*ceTI, RHCE*ceEK, RHCE*ceMO, and RHCE*ce733G to determine whether there is an association between the RHCE*ce733G mutation and the presence of these antigens.
Study
Design/Methods: A prospective observational study was performed by serologically testing donor samples of African Americans, identified through routine genotyping as having either variant or conventional RHCE*ce haploytpes, for the presence or absence of the V and VS antigens. Antisera for V and VS typing was obtained from the American Red Cross. Serological results were compared with the molecular genotype to determine if there is an association with the presence of the RHCE*ce733G mutation. A Fisher’s Exact Test was used to determine whether there is a correlation between the presence of the RHCE*ce733G variant and the presence of the V and VS antigens.
Results/Findings: Samples from 85 donors meeting the inclusion criteria were tested. Table 1 summarizes the identified genotypes and serological V and VS phenotype results. The Fisher’s Exact test showed that there is a significant relationship between the presence of the RHCE*ce733G mutation and the presence of both the V (p < .001) and VS (p < .001) antigens. Conclusions: Molecular genotyping can serve as a predictor of V and VS antigen presence if the RHCE*ce733G mutation is present. Since commercial antisera is not available for phenotyping for V and VS, alternative methods can assist immunohematology reference laboratories in providing suitable donor units for patients who form antibodies to V and VS. The e antigen has many variants, including V and VS, which are mainly found in the African population. Additional characterization of these variant antigens will benefit the transfusion medicine field and patients receiving transfusions.
