B(A) phenotype individuals have normal B antigen and a small amount of A antigen on the RBCs with anti-A in the plasma. Some highly potent monoclonal anti-A reagents are capable of agglutinating B(A) RBCs, which therefore usually results in a discrepancy between RBC and plasma ABO grouping. To date, five B(A) alleles (ABO*B(A)01, B(A)02, B(A)03, B(A)04, and B(A)05) have been defined by nucleotide sequences. To get a more complete picture of B(A) phenotypes found in the Chinese population and resolve blood donor typing problems caused by B(A) alleles, a serologic and molecular study of nine unrelated Chinese individuals and three families carrying B(A) alleles was conducted. Allele B(A)02 with a 700C>G mutation, allele B(A)04 with a single 640A>G substitution, and allele B(A)05 with a 641T>C mutation were detected in multigenerational families and unrelated blood donors. Neither the B(A)01 nor B(A)03 alleles with 703A>G substitutions were observed in this study. In addition, a polymerase chain reaction with a sequence-specific primer genotyping assay was developed for rapid identification of B(A)02, B(A)04, and B(A)05 alleles using genomic DNA samples. Immunohematology2007;23:69–74.
