BOW is a ‘new’ low-frequency red-cell antigen, detected in 2 unrelated English blood donors, that is sensitive to α-chymotrypsin and pronase. Anti-BOW is present in many polyspecific reagents used to define low-frequency antigens. Red-cell groups of the proposita, R.B., and her family show that the BOW blood group segregates independently from the ABO, Rh, MNSs, P(1) and Kell blood group systems.

The Skjelbred (Sk) antigen has been studied in the donor population of South London and found to have a frequency of 0.0035%. Its presence in serum as well as on red cells, its transient nature and its absence in relatives of Sk(+) individuals are suggestive of a non-genetic background for Sk. The antibody is not uncommon in normal donor sera (3-10%).