The B Allele With A 5 Center Dot 8kb Deletion In Intron 1 Of The Abo Gene Is The Major Allele In Japanese Individuals With B-M And A(1)B(M) Phenotypes

B-m and A(1)B(m) phenotypes are the most frequent ABO variants in the Japanese population. The B antigen on B-m red blood cells is only detectable by adsorption and elution tests, and plasma B-transferase activity is usually detected at half or less levels compared with that of common B. Recently, a B allele lacking an erythroid cell-specific transcription enhancer in intron 1 of the ABO gene was identified from individuals with B-m and A(1)B(m) phenotypes, which could explain the unique serologic properties of B-m. In the Japanese Red Cross Society, eight Blood Centers tested blood samples from donors throughout Japan and collected blood samples from 888 B-m and 415 A(1)B(m) individuals. DNA analysis revealed that 1300 of 1303 (9977%) individuals had the B allele with a 58kb deletion (c.28+5110_10889del), which included the enhancer element.