Abstract: Objective To study the genotype and molecular biological characteristics of 25 samples which showed B/AB subtypes. Methods The ABO*B alleles were identified by PCR-SSP or ABO exons 6-7/1-7 were analyzed by Sanger sequencing technology. Unidentified samples were further detected by PacBio:SMRT sequencing technology. Results Genetic sequence analysis of 25 B subtype /AB subtype samples revealed 7 known ABO*B alleles, namely ABO*BW.27 (3/25, 12.00%), ABO*BW.03 (5/25, 20.00%), ABO*B3.03 (2/25, 8.00%), ABO*BEL.03 (1/25, 4.00%), ABO*BW.07 (7/25, 28.00%), ABO*B3.05 (1/25, 4.00%), ABO*BW.12 (1/25, 4.00%). There were 5 unknown ABO*B alleles, of which 2 published but not included in ISBT were ABO*B.01 with c.28+5885C>T, ABO*B.01 with c.28+5875C>T. The other 3 were ABO*B novel alleles reported for the first time in this study, namely ABO*B.01(with c.3G>C)、ABO*B.01(with c.28+5862A>G)、ABO*B.01(with c.204-3C>G). Those have been compiled and published by Genebank. Conclusion The study clarified the molecular biological mechanism of 25 B/AB subtype cases and identified 5 novel ABO*B alleles. It enriches the ABO*B gene bank and provides a theoretical basis for better transfusion strategies.

Key words: ABO blood group, B variant, AB variant, Gene sequencing