[Molecular analysis of 23 cases of B subgroup].

To explore the molecular reasons of weak expression of B antigen on the red cell.Serological test for blood group was carried out, including red cell and plasma grouping, and anti-A1 and anti-H testing, and confirming weak A or B antigens by adsorption and elution. Exons 1-7 were sequenced directly, and one of them was cloned and sequenced.All of the 23 samples showed the weak B antigen by serological method. The alleles of the subgroups were identified by DNA sequencing, including 2 Bel subgroup, 4 B3 subgroup, 14 Bw subgroup, 2 CisAB subgroup and a novel allele. The novel allele showed a nucleotide substitution 662G>A in the exon 7, and the sequence was submitted to Blood Group Antigen Gene Mutation Database, and the novel allele was named Bel10.Nucleotide substitution in exon results in blood subgroup, which showed that the antigens were weakened, and Bw phenotype was the most frequently subgroup.