Abstract
Cromer‐related antigens, a series of blood group antigens phenotypically related to each other through various serological characteristics, have recently been shown to be carried on the complement regulatory glycoprotein decay‐accelerating factor (DAF). Cromer‐related antigens, therefore, represent a number of inherited variants and polymorphisms of DAF. The Inab phenotype, a ‘Cromer‐null’ phenotype in which the red cells lack all Cromer‐related antigens, appears to be an inherited DAF deficiency.