Abstract
BackgroundBlood group genotyping is increasingly utilized for prenatal diagnosis and after recent transfusions, but still lacks the specificity of serology. In whites, the presence of antigen D is predicted, if two or more properly selected RHD-specific polymorphism are detected. This prediction must fail, if an antigen D negative RHD positive allele is encountered. Excluding RHDψ and CdeS frequent only in individuals of African descent, most of these alleles are unknown and the population frequency of any such allele has not been determined.MethodsWe screened 8,442 antigen D negative blood donations by RHD PCR-SSP. RHD PCR positive samples were further characterized by RHD exon specific PCR-SSP or sequencing. The phenotype of the identified alleles was checked and their frequencies in Germans were determined.ResultsWe detected 50 RHD positive samples. Fifteen samples harbored one of three new Del alleles. Thirty samples were due to 14 different D negative alleles, only 5 of which were previously known. Nine of the 14 alleles may have been generated by gene conversion in cis, for which we proposed a mechanism triggered by hairpin formation of chromosomal DNA. The cumulative population frequency of the 14 D negative alleles was 1:1,500. Five samples represented a D+/- chimera, a weak D and three partial D, which had been missed by routine serology; two recipients transfused with blood of the D+/- chimera donor became anti-D immunized.ConclusionThe results of this study allowed to devise an improved RHD genotyping strategy, the false-positive rate of which was lower than 1:10,000. The number of characterized RHD positive antigen D negative and Del alleles was more than doubled and their population frequencies in Europe were defined.
Highlights
The antigen D encoded by the RHD gene is the most important blood group antigen determined by a protein
The most http://www.biomedcentral.com/1471-2156/2/10 frequent cause for the absence of the antigen D in whites is the lack of the whole RHD gene [10] due to a deletion occurring in the Rhesus box [7]
Most methods for antigen D prediction in whites probed the presence of RHD specific polymorphism [1,2,11,12,13]
Summary
The antigen D encoded by the RHD gene is the most important blood group antigen determined by a protein. Most methods for antigen D prediction in whites probed the presence of RHD specific polymorphism [1,2,11,12,13]. Two RHD positive antigen D negative alleles are frequent in Africans: RHDψ carries a 37 bp insertion at the intron 3/ exon 4 boundary and harbors a stop codon [14]; Cde s is a RHD-CE-D hybrid gene [15,16,17]. The presence of antigen D is predicted, if two or more properly selected RHD-specific polymorphism are detected. This prediction must fail, if an antigen D negative RHD positive allele is encountered. Excluding RHDψ and CdeS frequent only in individuals of African descent, most of these alleles are unknown and the population frequency of any such allele has not been determined
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