B(A)血型分子机制研究及其家系分析

目的 研究罕见B(A)血型的血清学特性和分子机制,为B(A)血型的临床输血提供理论基础.方法 利用单克隆抗体检测1例先证者、家系成员及献血者红细胞ABO血型抗原,用标准A、B、O红细胞检测其血清中的ABO抗体.采用盐水法、凝聚胺法和抗球蛋白法进行先证者与献血者交叉配合试验.采用PCR技术扩增ABO基因的第6、7外显子序列,对先证者、家系成员、献血者标本的ABO基因外显子6、7和侧翼内含子序列进行测序分析,并对先证者标本进行单倍体序列分析.结果 先证者及其2位家系成员红细胞上有A、B抗原,同时血清中存在抗A_1抗体,血清学表型为A_2B.直接测序分析发现先证者标本第6、7外显子存在261G/del、297A/G、526C/G、657C/T、700C/G、703A/G、796A/C、803G/C、930A/G杂合,可推断为B(A)_(02)/O_(01)基因型杂合子;家系中其母亲基因型为B(A)_(02)/B_(101),外祖母为B(A)_(02)/O_(01).先证者单倍体序列分析得到2个等位基因B(A)_(02)和O_(01);与B_(101)序列相比,B(A)_(02)位第700位C>G,导致1个氨基酸改变:第234位脯氨酸变成丙氨酸.既往血清学特性为A_2B的2个献血者,1个基因型为B(A)_(02)/O_(01),另1个基因型是A_(208)/B_(101).B(A)血型先证者与这2名献血者进行交叉配血试验均相合,临床输注后无不良反应.结论 α-1,3-半乳糖基转移酶等位基因(B等位基因)700C>G突变可导致形成B(A)血型,其血清学特性显示为A_2B表型.B(A)血型临床输血相配合的供者可选择A_2B表型的献血者.

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

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.