Molecular basis of the B(A)phenotype and its pedigree analysis

Abstract

Objective To investigate the serological characteristics and molecular basis of the B (A)phenotype in ABO blood group and provide the data for clinical transfusion of individuals with B(A) phenotype.Methods The ABO group antigens on red cells of the proband,family members and donors were identified by monoclonal antibodies and the ABO antibodies in sera were detected by the standard A,B,O cells.The compatibility testing for the proband and donors was detected by salted test,polybrene test and antiglobulin test.The coding region of exon 6 to exon 7 in ABO gene was amplified by polymerase chain reaction(PCR) and the PCR products were sequenced.The haplotypes of proband were analyzed by cloning and sequencing.Results It was showed that both A and B antigens were detected on red cells of the proband and her two family members,and there was anti-A_1 antibody in their sera.The serological phenotype of the samples are identified as the A_2B.DNA sequencing showed 261 G/del,297A/G,526C/G,657C/T,700C/G,703G/A,796C/A,803G/C,930G/A heterozygotes in exon 6 to exon 7.It can be deduced that genotype in the proband is B(A)_(02)/O_(01).The genotypes of her mother and grandmother-in-law were B(A)_(02)/B_(101) and B(A)_(02)/O_(01),respectively.After cloning and sequencing,two alleles B(A)_(02) and O_(01) in proband was showed.B(A)_(02) has snigle nucleotide change(700 C>G),which resets replacement of proline with alanine at position 234.Two donors with phenotype A_2B were identified as genotype B(A)_(02)/O_(01) and A_(208)/B_(101),respectively.The results of crossmatch testing is in accordane between the proband and two donors and there was no clinical adverse reaction after transfusion.Conclusions 700C>G in α-1,3galactosyltransferase allele(B allde)can result in B(A)phenotype in individuals with the phenotype of A_2B.The donors in the transfusion for the individuals with B(A) phenotype should include individuals with A_2B phenotype. Key words: ABO blood-group system; Blood group incompatibility; Pedigree