Molecular basis of the RHD gene in blood donors with DEL phenotypes in Shanghai

The purpose of the work was to analyse the genotype of D-elute (DEL) samples and to elucidate whether there were novel DEL alleles in Chinese population.

D-negative samples were identified by an indirect antiglobulin test (IAT), and absorption\elution tests to screen weak D, partial D and DEL phenotypes. DELs were further analysed by multiplex PCR, PCR-sequence-specific primers (PCR-SSP) and sequencing. Some of the DEL samples were determined to show RHD zygosity by PCR-restriction fragment length polymorphism or real-time quantitative PCR.

Of 400 253 samples from individual donations, 1585 (0.40%) were typed as D negative. Among these D-negative samples, 279 DELs were observed. Two hundred and sixty-eight DELs were confirmed to have the RHD (K409 K) allele. Three DELs seemed to have RHD-CE-D hybrid alleles, including one RHD-CE(4-9)-D, one RHD-CE(2-5)-D and one suspected RHD(1-9)-CE. Five novel RHD alleles were found among the rest of the DEL samples, including four RHD 3 g > a, one RHD (R10W), one RHD (L18P), one RHD (L84P) and one RHD (A137E). Eighty-four DELs were analysed for Rhesus box zygosity, there were 77 RHD+/RHD-and seven RHD+/RHD+.

About 4.35% apparent D negative Chinese individuals were weak D or partial D, while 17.60% were DEL. Novel DEL alleles are rare, and all but 11 of the 279 DELs were due to the most common DEL allele, RHD (K409 K). The RHD 3G > A might be the second most frequent DEL allele in Chinese. Exploration of a complete molecular basis for DEL in Chinese ethnic groups is a long-term endeavour.