MOLECULAR-BIOLOGY OF PARTIAL-D PHENOTYPES

We have examined all D-VI variant phenotypes submitted to the workshop by a combination of RT-PCR, multiplex RHD PCR and immunoblotting with Rh antipeptide sera. Our findings suggest that all DVT phenotypes ari se through hybrid RHD-RHCE-RHD genes. Genomic DNA derived from all DVT samples were shown to be RHD intron 4 negative when analysed with an RHD intron 4/exon 10 multiplex assay. We assume therefore that all D-V I phenotypes involve gene conversion events involving at least exons 4 and 5 of the RHD gene. Analysis of a novel D and E variant phenotype individual (ISBT49) by RT-PCR has allowed the identification of a hybr id Rh gene composed of exons 1-4 RHD: 5 RHCE/D and 6-10 RHD. We propos e that the partial D & E phenotype observed arises through D & E expre ssion on the hybrid RHD-RHCE-RHD protein: as no transcripts encoding R h E could be found.