Association of ABO gene mutations resulting in a rare B subgroup

Background and Objectives  B subgroups are rare and the genetic analysis reported to date has been limited. Materials and Methods  Serological and molecular investigations were performed in blood from a B-subgroup donor. Results  Red cells did not react with anti-B and anti-AB reagents. However, cells absorbed anti-B. Red cells presented positive reactions with anti-H, and saliva secreted H substance. The molecular study demonstrated a B allele with the substitutions 467C>T, 646T>A, 681G>A, 771C>T, 796C>A, 803G>C, 829G>A and an O allele with the sequence of O02. Conclusions  It is probable that the presence in exon 7 of some of the O02 substitutions could have weakened the enzymatic activity of the encoded B transferase.