Another example of a B variant.

A family in which five members has a weak B variant and one member had a normal A and weak B reaction is reported. It appears that these phenotypes arise by the inheritance of a variant allele of the ABO locus. Their cells react weakly when added to anti-B sera, and they have normal anti-A activity and an absence of anti-B in their sera. Additionally, all of the members tested had increased levels of cellular H substance and all of the affected secretor members of the family secreted normal amounts of both B and H substance. Transferase activity of the sera of these individuals confirmed the presence of the B-gene specific transferase.