Unexplained Appearance of Antibody in an Rhnull Donor

A blood donor of the phenotype Rh null was found at his 6th donation to have an antibody which had not been there before: he had never been transfused. The antibody reacts by the saline, albumin and enzyme methods but not by the antiglobulin (IgG). It reacted with all cells tested except the donor's own and those of two available Rh null people and, surprisingly, those of three available ‐D‐/‐D‐ people: it is apparently directed at the CcEe part of the Rh antigen complex. Like other Rh null propositi the donor has a compensated anaemia and his s and U antigens give some abnormal reactions. His parents are second cousins. Serological and pedigree evidence did not disclose his type of Rh null , ‘regulator’ or amorph.