A case of rare Del phenotype in a blood donor

Introduction. The highly immunogenic D antigen is one of the most important antigens after the group antigens A and B. Numerous alleles of the RHD gene lead to the emergence of new D antigen phenotypes. The Del phenotype is characterized by an extremely weak expression of the D antigen.

Aim: to present the results of D antigen typing in a blood donor with the Del phenotype.

Materials and methods. Two technologies were used for serologic typing of donor blood: microcolumn agglutination technology and solid phase microplate Capture technology. Primary genotyping of the donor was performed by allele-specific polymerase chain reaction (ASP-PCR). Nucleotide substitutions were searched for by Sanger sequencing of PCR products of exons of the RHD gene.

Results. When serological typing with IgM and IgG anti-D antibodies using solid-phase microplate technology was performed, a positive result was obtained. When determining partial variants of the D antigen, it was not possible to unambiguously interpret the data obtained. Molecular genetic analysis was required to identify variants of the weak D antigen. The results of primary genotyping by ASP-PCR suggested deletion of exon 9 of the RHD gene or nucleotide substitution in exon 9. According to the results of Sanger sequencing, a variant of the DNA nucleotide sequence c.1203T>A was detected in exon 9, resulting in the formation of the stop codon Tyr401Ter (rs759513820). This genetic variant corresponds to the RHD*01EL.17 allele. The antigen encoded by this allele is of the Del type.

Conclusion. It is necessary to use immunohematological methods in combination with molecular genetic methods for D antigen typing in blood donors with the Del phenotype in order to prevent alloimmunization with the D antigen.

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