Novel cisAB allele of the ABO gene with c.796A>C SNP in three Polish individuals

Routine ABO typing showed normal A and a very weak B antigens on RBCs of all three individuals (blood donor, her sister and one not-related patient). At samples from blood donor and the patient the B antigen was detected by tube technique only using anti-B clones: c.9621A8 (1+), G1/2 (weak+); the sera also contained anti-B antibodies(from 1+ to 2,5+). Commercial PCR-SSP kit revealed heterozygous A/B genotypes. The blood donor’s sister showed normal A (with all clones) and B antigen expression, but her genotype was revelead as heterozygous O2/B. In her plasma very weak anty-B was detected, but not anty-A. In all these individuals ABO sequencing of 7.21-kb fragment confirmed the heterozygous A/B or O2/B genotype, with ABO*A1.01 (or ABO*O2.01) and ABO*cisAB* allele (c.297A>G; c.526C>G; c.657C>T; c.703G>A; c.803G>C; c.930G>A) without c.796C>A polymorphism characteristic for ABO*B.01 allele.