AI Article Synopsis
- Discrepancies in ABO blood grouping can jeopardize patient safety due to factors like mixed-field agglutination, unusual alleles, or fetomaternal exchange, as seen in a case where a group A2 B mother had a baby typed as group O.
- Genomic DNA and red blood cells (RBCs) were analyzed, revealing the mother’s genotype as ABO*A1.01/B.01 and the baby’s as ABO*A1.01/O.01.01, with a notable genetic substitution impacting A antigen expression.
- A novel weak A allele (ABO*AW.29) was identified in this case, suggesting that the mother’s B-transferase may stabilize the altered A-transferase
Article Abstract
Background: Discrepancies in ABO grouping arise due to different reasons, posing a threat to patient safety. Underlying causes include mixed-field agglutination after transfusion, chimerism, fetomaternal exchange, or inheritance of unusual alleles resulting in weak A/B antigen expression. Cord blood from the infant of a group A2 B mother typed as group O, H+. Samples were investigated to elucidate this conundrum.
Study Design And Methods: Genomic DNA was analyzed by ABO genotyping and sequencing. Red blood cells (RBCs) were characterized by routine serology and flow cytometry. Glycosyltransferase structure was predicted with 3D-modeling software.
Results: The mother genotyped as ABO*A1.01/B.01, and the baby, ABO*A1.01/O.01.01. Sequencing revealed a substitution, 311T>A, in the ABO*A1-like allele, which predicts Ile104Asn. Flow cytometry demonstrated A antigen on the mother's RBCs equivalent to the A2 phenotype while no A was detectable on cord RBCs. However, blood from the 11-month-old child demonstrated markedly increased A expression, likely reflecting initiation of carbohydrate chain branching.
Conclusion: We unraveled a novel A(weak) allele (ABO*AW.29) in a case of apparent nonmaternity. Residue 104 is far from the catalytic site and may be involved in stabilizing the glycosyltransferase by dimerization. Our data support that the group AB mother's B-transferase stabilizes the altered A-transferase by heterodimerization, exemplifying the allelic enhancement phenomenon.
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Article Synopsis
- Discrepancies in ABO blood grouping can jeopardize patient safety due to factors like mixed-field agglutination, unusual alleles, or fetomaternal exchange, as seen in a case where a group A2 B mother had a baby typed as group O.
- Genomic DNA and red blood cells (RBCs) were analyzed, revealing the mother’s genotype as ABO*A1.01/B.01 and the baby’s as ABO*A1.01/O.01.01, with a notable genetic substitution impacting A antigen expression.
- A novel weak A allele (ABO*AW.29) was identified in this case, suggesting that the mother’s B-transferase may stabilize the altered A-transferase
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Division of Hematology and Transfusion Medicine, Department of Laboratory Medicine, Lund University, Lund, Sweden.
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