[Identification of a Bw14 subtype and exploration for its molecular basis]

To identify a rare subtype of the ABO blood group system and explore its molecular basis.

Based on a standard serological assay, ABO subtype and haplotype were analyzed through PCR amplification of the 7 exons and adjacent introns of the ABO gene and TA clone sequencing.

Forward typing showed a B type, while reverse typing demonstrated an extremely weak anti-B on routine gel analysis, which indicated a forward and reverse typing discrepancy. Absorption-elution testing confirmed that there was no A antigen on the surface of patient's red blood cells. Sequencing of the ABO gene showed a G>A exchange at position 523 in exon 7, which resulted in a Val to Met substitution at codon 175. Clone sequencing of the amplificons of the ABO gene showed an ABO* Bw14/O01 heterozygote genotype.

Molecular method is useful for the identification of ambiguous blood groups. A 523G>A substitution of the ABO gene resulting in a Bw14 subtype probably underlies the weak B phenotype noted in the patient.