A new human Duffy blood group specificity defined by a murine monoclonal antibody. Immunogenetics and association with susceptibility to Plasmodium vivax

The Duffy blood group system of human erythrocytes comprises a membrane glycoprotein recently characterized by immunoprecipitation techniques (1). It is a polymorphic system that includes determinants for five alloantigens, two of which are Mendelian alleles (Fya and Fyb) (2, 3). A null genotype, designated Fy(a b-) (4), lacks the expression of both Fya and Fy b, and is inherited as a third allele of the series . Homozygous Fy(a-b-) red cells, however, also lack expression of the Fy3 (5) antigen, which is present on all other Duffy types. Fy4 (6) occurs on almost all samples of Fy(a b-), but the expression is weak on some . In addition Fy4 is occasionally found on red cells of Fy(a +b'), so that its exact Duffy status is not in perfect agreement with the absence of both Fya and Fy b (7). Fy5 (8) resembles Fy3 but is also absent from Rh-null red cells regardless of their other Duffy types. These five specificities are inherited en bloc but they differ in their susceptibility to proteolytic enzyme treatment; the high frequency antigens Fy3, Fy4, and Fy5 being resistant to the effects of chymotrypsin, ficin, and papain, while Fya and Fy b are completely destroyed by these enzymes (7). Duffy maps to chromosome 1 (9) (i.e., is syntenic to Rh), which may be related to the peculiar absence of Fy5 on Rh-null cells. Interest in the Duffy system has been considerable since the demonstration by Miller et al . 776 J. Exp. MED