[Serological and Molecular Biological Analysis of a B(A) Subtype Family and Strategies for Safe Blood Transfusion]

Serological and molecular biological analysis of a B(A) subtype family was carried out to explore the underlying mechanism of B(A) subtype and clinical safe blood transfusion strategies.

The ABO blood type of the proband and her four family members were identified by serological methods, and serological experiments such as anti-H, anti-A1 and absorption-elution tests was added. In addition, the exons 6 and 7 of the ABO gene were sequenced by PCR-SSP (polymerase chain reaction - sequence specific primer).

The serological results showed that the agglutination intensity of the proband, her mother and her maternal grandmother was imbalanced during forward typing, showing weak A and strong B antigens, and there were strong H antigens and their intensity were higher than that of normal B type. The results of reverse typing indicated the presence of weak anti-A1 antibodies, and human anti-A was positive in the absorption-elution test. Genetic sequencing revealed a characteristic mutation of c.700 C>G in all three individuals. The sequencing results showed that the proband was B(A)02/B01, her mother was B(A)02/O02, and her maternal grandmother was B(A)02/O01 . According to the compatibility principle, 1.5 units of type O washed red blood cells were transfused intraoperatively, resulting in no adverse reactions.

The c.700 C > G mutation on exon 7 is the molecular basis for the formation of B(A)02, and pedigree analysis shows that the B(A)02 allele was inherited from the proband's maternal grandmother to the proband's mother and then to the proband, showing a stable cis-inheritance pattern rather than a spontaneous mutation. For patients with B(A)02 subtype, type O washed red blood cells and type AB plasma can be transfused according to the principle of compatibility.