Abstract:

Objective　 To study the frequency of weak B phenotype and analyze the molecular genetics on ABO gene, and to analyze the serological and genetic characteristics. Methods　 The samples with B phenotypes (moderately agglutinate by anti-B) were identified, screened and collected by the serological techniques in routine ABO blood group. The sequences of exon 6,exon 7and intron 6 of ABO gene were analyzed by direct DNA sequencing. Pedigree study was performed in traceable family. Results 　A total of 13 weak B phenotypes were observed in 241 952 cases (9 cases of blood group B and 4 cases of blood group AB). Enhanced agglutination with anti-H was observed in all the sample′s red cell. The ABO genotypes of A102/B_w12,B101/B101,B101/O02,A102/B101, B101/O01 were detected in 1,2,3,3 and 4 of the 13 cases. A same weak B phenotype was detected in a B101/O01 family (father) study. Conclusions 　The frequency of weak B phenotype in Fujian population with B blood group is about 1∶7 000. A B allele with a nucleotide 278C>T mutation (B_w12) is detected, and no mutation is detected among the others for exon 6, exon 7 and intron 6. Variations outside the sequence of glycosyltransferase catalytic domain may be the factors for weak B phenotype.

Key words: Weak B, B₂ subgroup, ABO blood group, ABO subgroup, Direct DNA sequencing