Molecular basis of the B(A) phenotype

Abstract

To explore the serological and molecular characteristics of a female with the B(A) phenotype and safety issues related to her blood transfusion. The B(A) phenotype of the proband was confirmed by serological testing. Her genotype was determined by using polymerase chain reaction-sequence specific primer (PCR-SSP) and direct sequencing of exons 6 and 7 of the ABO locus. Clinical condition of her blood transfusion was also reviewed. Both A and B antigens were detected on the red blood cells derived from the proband, while anti-A antibody was detected in her serum. The result of PCR-SSP suggested that she has a B/O02 phenotype. DNA sequencing revealed presence of 297A>G, 526C>G, 657C>T, 700C>G, 703G>A, 796C>A, 803G>C and 930G>A mutations. The genotype of the proband was deduced as B(A) 02/O02. Compared with the B101 allele, the B(A)02 allele has a nucleotide change (C>G) at position 700, which resulted in substitution of an amino acid (P234A). The result of cross match testing between the proband and two donors with an A2B phenotype was consistent. No adverse reaction was observed after the transfusion. 700G>C of B allele can result in the B(A) phenotype, which is similar to A2B. Blood donors for individuals with the B(A) phenotype should include those with an A2B phenotype.