The Duffy blood group system: a review of recent developments.

Five antigenic specificities are associated with the Duffy blood group system. Fya, Fyb, By3 and Fy4 are under the genetic control of a locus near the centromere of chromosome 1. Fy5 is absent from Fy (a-b-) red cells and also from cells that have the Rhnull phenotype. It appears that interaction between Duffy and Rh gene products may be necessary for synthesis of Fy5 antigen. Most Caucasians have a Fya or Fyb gene (or both), inherited by strict Mendelian principles. No evidence has been found to suggest that independently segregating Duffy modifying genes exist. The frequency of Duffy genes varies greatly in different sections of the world population. Aboriginal populations have a high frequency of Fya, Fyb is the most common gene in European Caucasians, and Negroes have a high frequency of an allele named Fy. Anti-Fya is the most common Duffy antibody and is found most frequently in the serum of Caucasians immunized by blood transfusion. The Fya antigen is about 40 times less immunogenic than K antigen of the Kell system. Only about one anti-Fyb serum is found foe every 20 that are anti-Fya. The Fya and Fyb red cell antigen receptors are inactivated by proteolytic enzymes but not by neuraminidase. Sialic acid does not appear to be an essential component of the antigen structure. Duffy antigens appear to be thermolabile membrane proteins and they are not present in a soluble form in plasma or in body secretions.