Programmpunkt

Titel: AN ABO*A286T>C Mutation Induces an AX/AWeak Phenotype
ID: PS-7-17
Art: Poster
Session:
ePoster-Session 6 – PS-7: Immunhämatologie und Immunologische Grundlagen II

Referent: Vanessa Scherer (Bad Kreuznach)


Abstract - Text

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Methods

AB0 blood groups were determined by standard automated routine serology (IH-500, BioRad, Munich, Germany). Molecular typing was performed by commercial PCR-SSP (ABO Type Variant, BAG Healthcare, Lich, Germany and RBD-Ready Gene ABO, Innotrain Kronberg, Germany). Genomic DNA sequencing covered amplification of the seven ABO exons including short flanking intron sequences and the promoter region followed by the electrophoretic separation in an ABI Prism 310 sequencer.

Results

Reverse blood grouping of a female patient did not match the ABO antigen determination. A missing agglutination of her RBC with Anti-A and Anti-B and a negative DAT was combined with a strongly reactive anti-B (++++) but only very weak or missing reactivity with A1 and A2 test cells. Commercial PCR-SSP clearly indicated the genotype O1A1 predicting the phenotype A1. DNA sequencing detected two alleles that can be assigned to an ABO*O1 (261delG) and a mutated ABO*A allele with a c.286T>C substitution inducing a Trp96Arg exchange. The mutation that clearly could be assigned to the ABO*A allele induces an impaired α1,3-N-acetyl-D-galactosaminyl-transferase activity and an Aweak or Ax phenotype. The mutation was submitted to GenBank (MT396943).

Background

A- and B-glycosyl-transferases specifically transfer carbohydrates to the H-antigen resulting in the blood groups A and B. Genetic variation of the ABO alleles may impair the enzymatic activity and transfer of the carbohydrates resulting in markedly reduced or even completely abolished A or B blood group expression. We describe the case of a mutation of the ABO*A101 reference allele that induces a strongly diminished blood group A expression.

Conclusion

This is another case of a new ABO mutation that induces an Aweak phenotype. DNA sequencing enables the determination of rare mutations that are not included in commercial genotyping assays.