The Genetic Polymorphism of RhD among Blood Donors in Gaza Strip and its Reflection on Blood Transfusion Strategy

Abstract

Rh system is one of the most and highly complex blood group systems, as many as over 45 different Rh antigens have been serologically defined. The Rh antigens are expressed by proteins encoded by a pair of highly homologous genes located at chromosome 1. RHCE gene encodes CcEe antigens, while the RHD encodes the D antigen. RhD is the most important, immunogenic and polymorphic Rh antigen from the clinical aspects (comprises at least 30 epitopes), which plays a key role in transfusion medicine. Anti-D antibodies remain the leading cause of the hemolytic disease of the newborn, and antigen D compatible transfusion is a standard practice in transfusion therapy. Partial D lacks one or more D epitopes, and the partial D individual could be immunized on exposure to normal D positive during blood transfusion or pregnancy. The DVI and DNB variants are the most frequent partial Ds that lack many of D epitopes, DVI is usually typed as D negative while DNB is typed as D positive. We have examined 102 genomic DNA samples derived from blood donors expressing D positive and negative phenotypes, to detect DVI and DNB variants, and to investigate the molecular genetic of Rh negative phenotype. In addition 3 samples with discrepant RhD (weak D) were also investigated. To detect DVI variant; simplex PCR was used to detect the presence or absence of RHD exon 10/intron 4, while PCR-SSP was used to detect DNB variant. Of these, 3 DVI and 3 DNB samples were detected between blood donors. The PCR observations indicated a complete deletion of RHD gene in D negative specimens, and that the 3 weak samples were similar to normal RHD alleles but probably with weak RHD expression. A full concordance between phenotype and genotype was observed in D positive samples.