The genetic and phenotypic basis of blood group A subtypes in Koreans

A serological and genetic study of Korean blood donors with phenotypic group A subtypes was performed. There were 176 donors with phenotypic A subtypes identified. Exons 6 and 7 from 57 representative donors were sequenced. The A^var allele (784 G > A) was cloned and sequenced, and a family study demonstrating its inheritance and unusual serological characteristics was performed. The A102 allele was the most frequently identified allele in phenotypically A₂ (58%, 11/19) and A₂B (68%, 17/25) donors. Anti-A₁ was rarely present amongst A₂ and A ₂B donors. The family study revealed that the A^var allele was expressed as phenotype A_weakB in A^var/B heterozygote members, but as phenotype O in A^var/O heterozygotes. The most frequent allele in Korean donors with the A₂ phenotype differs from its Caucasian counterpart, as does the frequency of anti-A₁. The A^var allele demonstrates allelic enhancement in A^var/B heterozygotes.