The D category VI type 4 allele is prevalent in the Spanish population.
BACKGROUND
The D category VI (DVI) is one of the clinically most important partial D. Three different molecular structures causing the DVI phenotype have been described.


METHODS
To determine the molecular basis of the DVI phenotype in the Spanish population, 20 DVI samples, previously detected in serologic screening, were examined by polymerase chain reaction with RHD exon-specific primers. Unexpected findings were further pursued by cDNA nucleotide sequencing.


RESULTS
A novel pattern of RHD exon amplification was detected, which did not correspond to any of the previously described molecular structures. The cDNA sequence led to the identification of the new hybrid RHD-Ce(3-5)-D allele. The origin of exon 2 is undeterminable, because the 5' breakpoint was located within a region of RHD and RHCE identical sequence, which encompasses this exon. Sequencing of intron 5 allowed the 3' breakpoint to be mapped between the sixth and seventh polymorphic sites. Serologically, the hybrid protein has a D epitope expression pattern identical to the previously described DVI phenotypes and an antigen density slightly lower than DVI type 3. The new DVI variant is linked to the DCe haplotype and expresses the low-incidence BARC antigen.


CONCLUSIONS
A novel structure causing the DVI phenotype, here named DVI type 4, has been characterized. This novel structure is the most frequent cause of DVI in Spain.
Immunohematology Service, Banc de Sang i Teixits, Barcelona, Spain.
Rosa
R
Esteban
Rosa
R
Montero
Willy A
WA
Flegel
Franz F
FF
Wagner
Laia
L
Subirana
Rafael
R
Parra
Anna
A
Ribera
Núria
N
Nogués
D001483:Base Sequence; D017931:DNA Primers; D005091:Exons; D014644:Genetic Variation; D006801:Humans; D007438:Introns; D008969:Molecular Sequence Data; D010641:Phenotype; D016133:Polymerase Chain Reaction / Q000379:methods; D012204:Rh-Hr Blood-Group System / Q000235:genetics*; D013030:Spain; D044465:White People / Q000235:genetics
D017931:DNA Primers; D012204:Rh-Hr Blood-Group System; C026410:Rho(D) antigen