Although the frequency of the new RHD alleles presented herein is low, their phenotypic and genotypic description adds to the repertoire of reported RHD alleles. These data can be useful for optimization of molecular screening tools.
Our data show that frequencies of aberrant RHD and RHCE alleles were similar, irrespective of location and ethnicity. In view of the predicted frequencies and relative clinical significance of both private antigens and high-prevalence antigens absent, the most relevant assays for individuals of African descent in a transfusion setting are for 1) partial RH2 in the patient and 2) RH54 (DAK) in the donor.
This report describes a novel RHCE mutation causing the loss of RhCE antigen expression in association with RHD deletion, leading to an amorph Rhnull phenotype.
Our survey indicated an uneven distribution of RH variant alleles between Dogon and Fulani, suggesting that study in well-documented cohorts is warranted. A high incidence of predicted partial-C phenotype encoded by RHCE*Ce-D(4)-ce was found in Fulani. Further study will also be needed to clarify the clinical significance of the new DIVa/ceTI(D2) haplotype encoding partial D and variant ce antigens.
Additional Supporting Information may be found in the online version of this article: Figure S1. Kaplan-Meier estimates of relapse free survival of patients grouped into low, medium and high-risk categories according to MRC scores.
Summary
Ethnic variations in red blood cell (RBC) antigens can be a source of alloimmunization, especially in migrant populations. To improve transfusion safety in continental Africa and countries with African migrants, we performed RBC genotyping to determine allele frequencies coding for high‐ and low‐prevalence antigens. A total of 481 blood samples were collected in ethnic groups from West, Central and East Africa. Molecular typing was performed using a polymerase chain reaction – reverse sequence specific oligonucleotide method. Results demonstrated no DI*1, DI*3, YT*2, SC*2, LW*7, KN*2 alleles in any sample and the CO*2 allele was rare. The frequency of LU*1 was comparable to that of European‐Caucasians (2%) except in Biaka pygmies (8%). The frequency of CROM*−1 was high in Mbuti pygmies (13%). High frequency of KN*7 and KN*6 may reflect selection pressure in the countries investigated. Analysis of Dombrock allele patterns confirmed uneven distribution of the DO*1 and DO*2 alleles with high frequencies of DO*−4 and DO*−5 in all groups. Altogether, findings demonstrated extensive allele‐frequency heterogeneity across Africa and suggested that knowledge of patient ethnicity gives information about the high‐prevalence antigens that may be lacking. These data are medically useful to support transfusion care of African migrants living in countries where the majority of the population is from a different ethnical background.
The D- - phenotype is a genetic variant of the Rh blood group system. It expresses D antigen but lacks C, c, E and e antigens. In D- - phenotype, the RHCE coding region is extensively modified by RHD sequence replacement, nucleotide deletion or splice-site changes. This article reports the identification of a new D- - haplotype in a Comorian man. It exhibits a hybrid gene in which RHCE gene exons 3-8 have been replaced by RHD sequences on the RHCE * C allele background. This allele is associated with no expression of c/C and e/E antigens and overexpression of RhD antigen.
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