Blood Group--En

Darnborough et al. (1969) discovered a new antibody, anti-En(a), which reacted strongly with many cells tested, a total of 7000, but did not react with her own cells or those of 2 of her 8 sibs. The proposita, an English woman, was pregnant and had been transfused 2 years earlier. En of the notation stands for envelope; the authors summarized as follows: 'The reactions of various unrelated blood group antigens are modified, in some cases enhanced and in others depressed, the total picture being strongly reminiscent of the effects of proteolytic enzyme treatment. It is suggested that these effects can only be due to some factor affecting the red cell structure possibly by modifying the cell envelope.' Two further examples of En(a-) were found in Finland in unrelated persons. The great rarity of the phenotype is indicated by the fact that by 1975 only these 3 families had been discovered (Race and Sanger, 1975). The English case had parents from a small fishing port in Yorkshire. The parents of both Finnish probands were consanguineous. Because of the consanguinity, any locus for which the En(a-) persons were heterozygous cannot have been responsible for the En gene. Using this reasoning, ABO, MNSs, Rh, Duffy, Haptoglobin, Kidd, Gm, and Dombrock could be excluded (Race and Sanger, 1975). Although En is independent of MN, MN typing shows a profound derangement in En(a-) persons.