[Identification and analysis of a case with Bw11 subtype]

To analyze serological and molecular characteristics of a case with Bw11 subtype.

The ABO antigen and antibody in serum were respectively detected with the classical tube method, microcolumn gel method, and absorption and diffusion method. The ABO genotype was determined with PCR using sequence-specific primers (PCR-SSP). Exons 1-7 of the ABO gene were analyzed by Sanger sequencing. Haplotype analysis was carried out for exons harboring variants.

Forward and reverse typing with the microcolumn gel method has suggested type O, while forward and reverse typing with the classical tube method yielded inconsistent results. Absorption and diffusion test confirmed presence of B antigen. Antibody screening excluded presence of alloantibodies. The result of PCR-SSP suggested a B/O1 genotype.A 695T>C variant was identified in exon 7 as compared with the B101/O01 allele, which resulted in conversion of Leucine to Proline at position 232, and was confirmed as Bw11/O1 heterozygote.

The nt695T>C variant probably underlay the weakening of B antigenin the individual. There may be strong anti-B antibodies in Bw11 subtypes. Human-derived and certain monoclonal reagents may not detect Bw11 subtypes which is easy to be misjudged as type O. Application of molecular methods can identify ABO subtypes with accuracy.