title: DAR, a new RhD variant involving exons 4, 5, and 7, often in linkage with ceAR, a new Rhce variant frequently found in African blacks.
abstract: The highly polymorphic Rh system is encoded by 2 homologous genes RHD and RHCE. Gene rearrangements, deletions, or point mutations may cause partial D and CE antigens. In this study, a new RHD variant, DAR, and a new RHCE variant, ceAR, are described in 4 Dutch African Blacks. Serologically, DAR showed weaker reactions with a monoclonal antibody and polyclonal antiserum against D. The DAR phenotype was characterized by complete loss of at least 9 of 37 Rh D epitopes. Erythrocytes expressing ceAR were all typed as VS(-), V(+). DNA analysis showed a partial D allele with only 3 mutations: C602G (exon 4), T667G (exon 5), and T1025C (exon 7). The ceAR allele carried G48C (exon 1), a hybrid exon 5 (A712G, C733G, A787G, and T800A), and A916G (exon 6). To study the frequency of these variants, 326 South-African Blacks was screened genomically. Of the 326 donors, 16 (4.9%) carried the DAR allele, 20 (6.1%) the ceAR allele, and 14 (4.3%) both mutated alleles. Five of these donors (1.5%) had the DAR phenotype, indicating that they carried the DAR allele homozygously or next to a D-negative allele. Immunogenicity of the D antigen for individuals with the DAR phenotype was proven, because 1 of the 4 Dutch individuals produced allo-antibodies against D after multiple transfusions with D-positive blood. In a multiethnic society, the prevalence of this D phenotype will increase and is therefore relevant in transfusion practice and in prevention of hemolytic disease of the newborn.
authors.affiliation: Laboratory for Transfusion Science, Bloodbank Rotterdam, Rotterdam, The Netherlands.
authors.forename: M B
authors.initials: MB
authors.lastname: Hemker
authors.forename: P C
authors.initials: PC
authors.lastname: Ligthart
authors.forename: L
authors.initials: L
authors.lastname: Berger
authors.forename: D J
authors.initials: DJ
authors.lastname: van Rhenen
authors.forename: C E
authors.initials: CE
authors.lastname: van der Schoot
authors.forename: P A
authors.initials: PA
authors.lastname: Wijk
mesh_terms: D000349:Africa; D000483:Alleles; D044383:Black People; D005091:Exons; D015321:Gene Rearrangement; D006801:Humans; D012204:Rh-Hr Blood-Group System / Q000235:genetics*; D017422:Sequence Analysis, DNA
chemical_list: D012204:Rh-Hr Blood-Group System