LAUSR

The genetic basis of ABO was elucidated by Yamamoto and colleagues through isolation, purification, cloning, and sequencing of cDNA encoding the A1 glycosyltransferase, and subsequently of cDNAs encoding other major ABO alleles were characterized. RBCs with the A2 phenotype are typically strongly reactive with anti-A and nonreactive with anti-A1 lectin. Most A allele are distinguished from the A consensus allele by two nucleotide differences, c.467C>T and c.1061delC. The use of ABO genotyping for resolving serological discrepancies has led to the identification of more than 245 alleles, including 16 to date that appear to have arisen by additional changes on the A background associated with a weak A phenotype (International Society of Blood Transfusion website [v1.1 171023]). Here, we report four novel A alleles found in six samples referred for ABO genotyping following discrepant serological findings.